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MAS OTBCFS M TM THBRMIL BEOGMPOSUIOH
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BASS EFFECTS ON THE THERMAL DECOMPOSITION
OF sec-3UTYLLITHIUM SOLUTIONS
THESIS
Presented to the Graduate Council of the
North Texas State University in Partial
Fulfillment of the Requirements
For the Degree of
MASTER OF SCIENCE
By
George Michael Adams, B. S.
Denton, Texas
June, 1966
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TABLE OF CONTENTS
Page
LIST OP TABLES iv
LIST OP ILLUSTRATIONS . . v
Chapter
I. INTRODUCTION 1
Colligative Properties Structure of Allcyllithium Compounds Pyrolysis of Alkyllithium Compounds
II. EXPERIMENTAL 14
Preparation of Lithium Sand Preparation of sec-Butyllithium Preparation of Lithium Alkoxides Purification of seckButyllithium Preparation of Pure1 and Base-Added sec-
Butyllithium Solutions Thermal Decomposition of sec-Butyllithium
Solutions Analysis of G-aseous Products Product Distribution Versus Time
III. RESULTS AND DISCUSSION 34
APPENDIX A 46
APPENDIX B 55
BIBLIOGRAPHY 6 ?
i n
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LIST OF TABLES
Table Page
I. Association Numbers of Organo-Lithium
Compound 2
II. Differences in ?<*> Observed and Calculated . . . . 27
III. Pyrolysis of sec-Butyllithium Solutions 37
IV. Average Product Distribution Versus the Alkoxide Moiety 4-0
V. Elimination Reaction Products Distribution for sec-Butyl Systems 41
xv
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LIST OP ILLUSTRATIONS
Figure Page
1. Brown's Proposed Ethyllithium Tetramer
and Hexamer . 4
2. Eastham's Proposed Etherated Dimer 6
3. Distillation Vessel 20
4. Decomposition Vessel 20
5. Vacuum System 21
6. A Typical Pressure Versus Time Plot for
Decomposition Gases 26
7. Gas Chromatogram of Pyrolysis Gases 30
8. Product Distribution Versus Time 31 9. Graph of Log (k0"bs) Versus Log (B) 39 10. Possible Transition State Leading to 1-Butene . . 41
11. Possible Transition State Leading to 2-Butene . . 42
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CHAPTER I
INTRODUCTION
Colligative Properties
Alkyllithium compounds, first extensively studied by
Schlenk and Holtz (17) in 1917, exist in both solid and
liquid states at room temperature. Methyl, ethyl, and
isopropyllithium are solids and the higher homologs are
liquids at room temperature except where symmetrical alkyl
branching occurs as in the cases of tert-butyl and neo-
pentyllithium which are solids. With the exceptions of
methyl and phenyllithium, the solids can often be sublimed
and the liquids, distilled providing both processes are
carried out in high vacuum and at high temperatures (6).
Alkyllithium compounds, except methyllithium, are soluble
in non-polar solvents such as benzene, cyclohexane, and
n-hexane and in polar solvents such as ethyl ether and
dioxane (6). These properties are quite different from cor-
responding organo-sodium, -potassium, -rubidium, and -cesium
compounds which are insoluble in non-polar solvents and de-
compose upon attempted purification.
In 1951 V/ittig (22) first reported that alkyllithium
compounds were associated species and since then many com-
pounds have been studied. The association numbers for a few
1
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TABLE I
ASSOCIATION NUMBERS OP ORGANO-LITHIUM COMPOUNDS
Compound Solvent i Reference
jZfLi Et20 (b)* 2 (22)
0CH2Li Et20 (b) 2 (22)
C2H5IrfJ 0E 6 (14) n-Ci2H25ii' 0E 2 (14)
C2H5Li 0E 6 (3)
C2H5Li vapor 4 6 (1) C2H5Li Cyclohexane 6 (4)
t-BuLi 0E 4 (20) t-BuM Hexane 4 (20)
n-Buli Cyclohexane 4 (7) n-Buli Et20 2 (7) n-BuLi Cyclohexane 6 (12) n-BuLi 0E 6 (12)
C2H5Li crystal 4 (8)
CH^ii crystal 4 (21)
Poly- 0E 2 (13) styrenyl- Hexane 2 (13) lithium THF 1 (13)
Dioxane 1 (13)
Polyiso- 0E 2 (13) propenyl- Hexane 2 1 3
lithium THP 1 13) Dioxane 1 (13)
*(b) boiling
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alkyllithium compounds are shown in Table I. The association
number is a function of both the solvent polarity and branch-
ing of the organic moiety. In polar solvents association
numbers of one and two are found and in non-polar solvents
association numbers of four and six are found. In non-polar
solvents the symmetry of the organic moiety directly affects
the association number, as exemplified by n-butyllithium
(n-Buli), which is a hexamer, and tert-butyllithium (t-BuLi),
which is a tetramer. Only in the case of large or macro-
molecules are monomeric species found,and only in polar
solvents (13).
Structure of Alkyllithium Compounds
The structure of alkyllithium compounds has been a
point of conjecture for many years. Rundle has proposed an
electron-deficient or delocalized bonding theory to account
for the crystal structures of the tetramethylplatinum tetramer,
the trimethylaluminum dimer, and the dimethylberyllium polymer,
which are similar types of compounds. The theory predicts
that delocalized bonding occurs when "an atom (usually
metallic) with more low energy orbitals than valence electrons
[is] combined with atoms or groups containing no unshared
electron pairs . . . . It appears that under these circum-
stances derealization of bonding occurs so as to use all of
the low energy bonding orbitals of the metallic atom" (16,
p. 46). Brown and his coworkers (1, 2) applied this bonding
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principle to predict the geometry of the ethyllithium
(EtLi) tetramer and hexamer observed in the mass spectrum
of ethyllithium vapor. The proposed structures are shown
in Figure 1.
Pig. 1—Brown's proposed ethyllithium tetramer and hexamer.
Weiner, Vogel, and West (20) in 1962 proposed the same
type of structure for the tetramer of tert-butyllithium. In
the proposed structure four center electron deficient bonds
involving unspecified orbitals of three lithium atoms and the
sp^ orbital of one alpha carbon atom are proposed. In the
tetramer four equivalent delocalized bonds would be found.
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Eastham, on the other hand, has proposed for the n-
butyllithium tetramer " . . . that a symmetrical tetramer
is formed "by quadripole association of two dimers, i.e.,
two (BuLi)2 units . . ., face-to-face, with the Li-Li axis
of one orthogonal to that of the other" (7, p. 3519). Thus
two choices, delocalized "bonding or ionic association, can
"be used to explain the structure of alkyllithium compounds.
Dietrich (8) in 1963" published his findings concerning
the crystal structure in ethyllithium. He found that the
crystalline substance was tetrameric, appeared to be two
associated dimers, and that all carbon-lithium distances
were not equivalent (11, p. 5). In essence his data con-
firmed the cyclic structures proposed, but showed that the
tetrahedron of lithium atoms was distorted.
Weiss (21) in 1964 published his findings concerning
crystalline methyllithium. By interpreting x-ray powder
patterns he deduced that solid methyllithium was tetrameric
and that all the carbon-lithium distances were equivalent,
2.27-A. He noted that the lithium skeleton formed a perfect
tetrahedron and equidistant over each face of the tetrahedron
was a methyl group. The rather short Li-Li distances observed
for methyllithium tetramers would seem to indicate that a
delocalized description of the bonding is to be preferred.
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Eastham (7) has proposed that in the presence of
ether the n-butyllithium tetramer* breaks down to ether
solvated dimers as shown below:
6 -CH,
CK. 6+
CII
CH CH
c3h7
Pig. 2—Eastham1s proposed etherated dimer
Brown and coworkers (3) have shown that the addition of
triethylamine to ethyllithium does not disrupt the hexamer
structure if the base hexamer ratio is less than 3.5; as
the ratio is increased, however, the hexamers break down
to complexed dimers. Brown, Ladd, and Newman (4) have
shown that lithium ethoxide does not break up the hexamer
of ethyllithium. At high lithium ethoxide to hexamer
ratios they have proposed that clusters of the base are
coordinated to the hexamer framework.
*The discrepancy between the association numbers re-ported for n-butyllithium in cyclohexane (i = 4 or 6) by two groups of workers has not been explained at this writing (cf. Table I).
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Pyrolysis of Alkyllithium Compounds
Schorigin (18) in 1910 thermally decomposed ethyl-
lithium and obtained ethane, ethylene, and lithium
hydride. In 1933 Thompson and Stevens (19) thermally
decomposed ligroin solutions of ethyllithium and obtained
the same gaseous products and a solid which upon hydrolysis
yielded an amount of hydrogen corresponding to the solid,
being 50 per cent lithium hydride.
Ziegler and Sellert (23) obtained generally the same
results when they thermally decomposed ethyllithium and
n-butyllithium. Analysis of the hydrocarbon products
obtained when n-butyllithium was thermally decomposed in
an autoclave showed 92 per cent 1-butene and up to 8 per
cent n-butane. A solid resinous product was also found.
These results were interpreted in terms of the following
reactions:
CH3CH2CH2CH2Li > CH3CH2CH=CH2 + LiH , [l]
CH5CH2CH=CH2 + C4HgLi — • CH5gCH=CH2 + C 4H 1 0 [2]
GH-5CHCH=0H2 > CH2=0HGH=CH2 + LiH [3] I»i I
1 > polymer
Initially only l-bute;ne was formed [Y] . As the reaction
proceeded, some of the 1-butane. reacted with the n-butyllithium
[2] to produce the observed butane. The resin would come
from the butadiene jV] , which is known to polymerize in the
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8
presence of alkyllithium compounds. Whenever the decom-
position was carried out so as to remove the gases as they
were formed, pure 1-butene was the only gaseous product.
Boiling solutions of n-butyllithium in n-octane yielded 95
per cent 1-butene and 5 per cent n-butane. Weiner, Vogel,
and West (20) obtained 94 per cent isobutylene and 6 per
cent isobutane by refluxing solutions of tert-butyllithium
in n-heptane.
Bryce-Smith (5) decomposed n-butyllithium in isopropyi-
benzene at 135°C and obtained butane, 1-butene, and lithium
hydride. The absence of coupling products was interpreted
to mean that the reaction did not proceed through a free
radical pathway.
In 1965 Lin (11) showed that when pure ethyl, isopropyl,
and n-butyllithium were thermally decomposed in such a fashion
as to insure the removal of the product gases, the olefins
were the main products, 99-100 per cent, and only trace
quantities of the saturated hydrocarbons were found, sec-
Butyllithium was decomposed in the same manner and found to
yield about 33 per cent 1-butene, 50 per cent cis-2-butene,
and 17 per cent trans-2-butene. The product distribution was
found to be only slightly dependent upon the decomposition
temperature in the region 78-104° C. All the decompositions
were found to be first order in product gases, and Arrhenius
plots of the temperature dependence yielded the activation
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parameters. Lin proposed that the decomposition proceeds
via a cis-elimination pathway from the sterically hindered
polymeric alkyllithium species. The favored cis-orientation
of the proposed sec-butyllithium tetramer was used to explain
the unprecedented high per cent cis-olefin observed. Glaze,
Lin, and Felton (9) have shown that the apparent stereo-
specificity of the decomposition of sec-"butyllithium is lost
when solutions in n-octane are decomposed.
Kutta (10) studied the thermal decomposition of solutions
of n-butyl, isobutyl, tert-butyl, and sec-butyllithium. He
found that olefins and lithium hydride were the primary re-
action products. It was determined that all the decompositions
except sec-butyllithium were first order, and Arrhenius plots
were made to determine the reported activation parameters.
The kinetic iostope effect for the decomposition of Q , § -
dideutero-n-butyllithium (kg/kj) = 2.96) was interpreted in
favor of a cis-elimination mechanism. Kutta (10) also showed
that the rate of decomposition of n-butyllithium solutions
was unaffected by excess lithium hydride and variations in
the stirring speed. In addition it was shown that the rate
constant for the decomposition of n-butyllithium solutions
was increased when lithium n-butoxide was added, and that the
increase was a linear function of the amount of base present
in solution. The rate data for sec-butyllithium were found
to follow neither first nor second order rate laws, and no
order was determined.
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10
The pyrolysis of sec-butyllithium in solution was
studied in an attempt to understand the loss of stereo-
specificity and the atypical kinetics that have "been
reported. Additionally, the effect of added lithium
alkoxides was studied to determine their effects on the
highly reactive sec-hutyllithium substrata.
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CHAPTER BIBLIOGRAPHY
1. Berkowitz, Joseph, D. A. Bafus, and Theodore L. Brown, "The Mass Spectrum of Ethyllithium Vapor," Journal of Physical Chemistry, LXV (ig61), 1380.
2 B r o w n , Theodore L., D. V/. Dickerhoof, and D. A. Bafus, "The Infrared and Nuclear Magnetic Resonance Spectra of Ethyllithium," Journal of the American Chemical Society, LXXXIV (19^2), 1371.
3. Brown, Theodore L., R. L. Gerteis, D. A. Bafus, and J. A. Ladd, "Interaction of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Triethylamine in Benzene," Journal of the Ameri-can Chemical Society, LXXXVI (1964), 2155.
4. Brown, Theodore L., J. A. Ladd, and G. N. Newman, "Inter-action of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Lithium Ethoxide in Hydrocarbon," Journal of Organometallic Chemistry, III (1965), 1»
5. Bryce-Smith, D., "Organometallic Compounds of the Alkali Metals. Part V. The Non-Radical Decomposition of n-Butyllithium," Journal of the Chemical Society, (1955),1712.
6. Coates, G. E., Organo-Metallic Compounds, New York, John Wiley and Sons, Inc., 1$56.
7. Cheema, Zafarullah K., G. W. Gibson, and J. 3?. Eastham, "The Structure of Butyllithium in Ether: A Solvated Dimer," Journal of the American Chemical Society, i n n (i9b'i), 351?. ^ '
8. Dietrich, H., "Die Kristallstruktur von Athyl-Lithium," Acta Crystallographica, XVI (1963), 681.
9. Glaze, William H., Jacob Lin, and E. G. Felton, "The Thermal Decomposition of sec-Butyllithium," Journal of Organic Chemistry, XXX (1965), 1258.
10. Kutta, H. W., "The Pyrolysis of Alkyllithium Compounds in Solution," unpublished master's thesis, Department of Chemistry, Ohio State University, Columbus, Ohio, 1964.
11
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11. Lin, Jacob, "Thermal Decomposition of Alkyllithium Compounds in the Pure State," unpublished master's thesis, Department of Chemistry, North Texas State University, Denton, Texas, 1965.
12. Margerison, D. and J. P. Newport, "Degree of Association of n-Butyllithium in Hydrocarbon Media," Transactions of the ffaraday Society, LIX (1963), 2058.
13. Morton, Maurice, I. J. Fetters, and R. A. Pett, "Association of Organolithium Macromolecules'un-published paper read before the Second International Symposium on Organometallic Chemistry, Madison, Wisconsin, August 30, 1965.
14. Rodionov, A. 1., D. N. Shigorin, and T. V. Talalaeva, "A Study of the Structure of Complex Aliphatic Organic Lithium Compounds," Doklady Akademii Nauk, English translation, CXXXXIII (1962), 175.
15. Rogers, M. T. and A. Young, "The Electric Moment of n-Butyllithium and the Nature of the Lithium-Carbon Bond," Journal of the American Chemical Society, LXVII (194b), 27T8T
16. Rundle, R. E., "Electron Deficient Compounds," Journal of Physical Chemistry, LXI (1957), 45.
17. Schlenk, W. and J. Holtz, "Uber die einfachsten Metall-organischen Alkiliverbindungen," Berichte Per Deutschen Chemischen Gesellschaft, L (1§17), 262.
18. Schorigin, P., "Uber die Natriumalkyle und ihre Reaktion Mit den Atheru," Berichte Der Deutschen Chemischen Gesellschaft, XXXXIII (1"9W7 1'"
19. Thompson, T., and T. S. Stevens, "Organic Compounds of Boron," Journal of the Chemical Society (1933), 5 5 6 ^
20. Weiner, Michael, George Vogel, and Robert West, "The Physical Properties and Structure of t-Butyllithium," Inorganic Chemistry, I (1962), 654.
21. Weiss, E. and E. A. C. Lucken, "Die Xristall- und Elektronenstruktur des Methyllithiums," Journal of Organometallic Chemistry, II (1964), 197.
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22. Wittig, G., F. J. Meyer, and G. Lange, "liber das Verhalten von Diphenylmetallin als Komplexbildner Justus liebigs Annalen der Chemie, DLXXI (1951), X F r : .
23. Ziegler, K. and H. G. Gellert, "The Thermal Stability of lithium AlkyIs," Annales de Chimie, DLXVII (1950), 179.
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CHAPTER II
EXPERIMENTAL
Preparation of Lithium Sand
Reagents
Mineral oil, light viscosity Lithium metal (99 *7 per cent lithium containing 2 per cent
sodium (2) ) Sodium oleate, reagent grade n-Pentane, 99 mole per cent minimum purity
Procedure
About 100 milliliters of mineral oil was poured into
a dry 250 milliliter Erlenmeyer flask with a ground glass
stopper neck. To this was added 7-7 grams of finely divided
one-half inch lithium rod and a small amount of sodium oleate,
a dispersing agent.
The loosely stoppered flask was placed on a hot plate
regulating at maximum setting. As heating proceeded the
stopper was frequently loosened to prevent it from blowing
out. Heating was continued until silver balls of molten
lithium metal were observed. The tightly stoppered flask
was removed from the hot plate and vigorously shaken in
front of a compressed air jet.' After the contents were cool
enough so that agglutination of the metal particles could not
occur, shaking was stopped and the contents allowed to cool
to room temperature. 14
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15
l
About 200 milliliters of n-pentane was added to the
cooled flask and the contents transferred to a Buchner
funnel and rapidly filtered. The flask was rinsed with
n-pentane to assure a quantitative transfer. The finely
divided sand was sucked dry and quickly transferred to a
reaction vessel which had previously been flushed with
argon gas.
Preparation of sec-Butyllithium
Reagents
Lithium sand, containing 2 per cent sodium sec-Butyl chloride, Eastman reagent grade n-Pentane, 99 mole per cent minimum purity Xrgon gas, 99*997 per cent purity
Procedure
The preparation was carried out under an argon gas
atmosphere in a three-necked, 500 milliliter, round-
bottomed flask equipped with a Hirschberg stirrer and Teflon
stirring gland, Priedrichs reflux condenser, and a 250
milliliter addition funnel.
Lithium sand, 7.7 grams (1.1 moles), and 100 milliliters
of n-pentane were placed in the flask. Sec-butyl chloride,
53.1 milliliters (0.5 mole), and 100 milliliters of n-pentane
were mixed and placed in the addition funnel. Stirring was
started and the flask contents were brought to a slow reflux
by raising a warm heating mantle around the flask. After
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16
reflux had begun, 10 per cent of the sec-butyl chloride
solution was added to the reaction flask. When a definite
color change to purple or blue was noted, slow dropwise
addition of the sec-butyl chloride solution was started and
the external heat source removed.
Addition was completed in a 3-4 hours and the flask
contents brought to reflux with a heating mantle. Reflux
was maintained for two hours. The flask was then cooled to
room temperature, securely stoppered, and taken into a dry
box. (The contents were filtered through a medium frit
Buchner funnel into a 250 milliliter Erlenmeyer flask equip-
ped with a ground glass stopper neck. Successive washings
of the blue residue with n-pentane were needed to assure
good yields of sec-butyllithium. The clear n-pentane solution
was concentrated by removing the solvent under vacuum. After
the solution was concentrated as much as possible, the flask
was stoppered and the clear to yellow solution was stored for
later use.
Preparation of lithium Alkoxides
Reagents
Lithium dispersion, 30 per cent in wax, Lithium Corporation of America
Ethyl alcohol, absolute, redistilled sec-Butyl alcohol, reagent grade PKenol, reagent grade Benzene, thiophene free, redistilled n-Pentane, 99 mole per cent minimum purity
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17
Procedure
The benzene and n-pentane were distilled from lithium
aluminum hydride to assure dryness. The ehtyl alcohol was
distilled from magnesium metal to assure dryness.
Thirteen grams of the lithium dispersion were taken
into the dry "box, dispersed in about 400 milliliters of
n-pentane, and filtered. The cleaned, micron-size lithium
particles and 125 milliliters of n-pentane were placed in a
three-necked, 500 milliliter, round-bottomed flask equipped
with a Hirschberg stirrer and Teflon stirring gland in the
center neck and two ground glass stoppers in the side necks.
The stoppered flask was brought out of the dry box and fitted
with a 250 milliliter addition funnel and a Priedrichs con-
denser. The flask was initially flushed with argon gas and
an argon gas blanket was maintained during the entire re-
action. Cold water was circulated through the condenser from
an ice-water reservoir with a circulating pump.
A mixture of 0.6 mole of alcohol in 100 milliliters of
solvent (ethyl alcohol and benzene, sec-butyl alcohol and
n-pentane, or phenol and benzene) was placed in the addition
funnel. Stirring was started and about 10 per cent of the
contents of the addition funnel were added. The system
warmed, gas was evolved, and when a slow reflux was reached,
addition was initiated to maintain the reflux rate. Total
addition time was from four to eight hours. When benzene was
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18
used as a solvent the system was heated gently with a heating
mantle during the entire reaction. After addition was com-
pleted the system was heated at vigorous reflux for an
additional two to six hours. The system was then cooled to
room temperature, securely stoppered, and taken into the dry
box.
The flask contents were transferred to a 250 milliliter
Srlenmeyer flask and the solvent removed "by vacuum distil-
lation. The resulting solid was transferred to a 100
milliliter, single-neck, round-,bottomed flask. The flask
was stoppered with a stopcock adapter and "brought out of
the dry box. The flask with adapter was fitted onto a
vacuum line to which another flask submerged in a Dewar of
liquid nitrogen was attached. The flask containing the
alkoxide was heated at 100°C for four to six hours to drive
off any remaining solvent or alcohol. The flask was taken
back into the dry box and the adapter replaced with a glass
stopper. The alkoxide was stored for later use.
Lithium ethoxide and phenoxide were white crystalline
solids, while lithium sec-butoxide was a light grey crystal-
line solid.
Purification of sec-Butyllithium
Reagents
sec-Butyllithium, crude n-Octane, 99 mole per cent minimum purity, redistilled
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19
Procedure
The apparatus shown in Figure 3, page 20, was used to
distill the crude sec-buty H i thium on a vacuum line as shown
in Figure 5, page 21.
In the dry box, 5-7 milliliters of the crude sec -
butyllithium was pipetted into the 50 milliliter bulb of
the distillation apparatus. A few glass beads were added
to prevent severe bumping during the subsequent distillation.
The sidearm, was stoppered with a glass stopper and the U-tube
was stoppered with a vacuum stopcock adapter. The apparatus
was brought out of the dry box and fitted onto the vacuum
line. The bulb was frozen in liquid nitrogen, the system
evacuated, and the side-arm torched off at point a.
The bulb contents were allowed to warm slowly to room
temperature under vacuum. After reaching room temperature
the entire system was evacuated until a minimum pressure of
50 microns was noted on the McLeod gauge. Y/hile the system
was evacuating the arm between the bulb and the U-tube was
wrapped with heating tape.
When the minimal pressure was reached, a Dewar of liquid
nitrogen was raised around the U-tube and an oil bath at
100-105°C was raised around the bulb. The heating tape was
turned on and set to heat at about 90°C. Distillation began
immediately. The bulb was thumped occasionally to prevent
severe bumping. Two or three times during the distillation
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20
Pig. 3—Distillation vessel
Pig. 4—Decomposition vessel
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<0 CO 3 <£ CD
21
a 0
CD
CO
3 0 03
1 IA
•H £4
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22
tile Dev/ar of liquid, nitrogen was lowered and the pure
sec-butyllithium which, had frozen in the arm of the U-tube
was allowed to warm slightly and flow into the bottom of
the U-tube. The bulb was distilled to dryness and then the
oil bath removed. The Dewar was lowered and the pure sec-
butyllithium warmed to room temperature. While the sec-
butyllithium was warming the heating tape was removed and
the system evacuated for about thirty minutes to remove
any condensed decomposition gases arising from a partial
decomposition of the crude sec-butyllithium during distil-
lation.
The distillation apparatus was removed from the vacuum
line and taken into the dry box. The vacuum stopcock adapter
was removed and about five milliliters of n-octane was pipetted
into the U-tube. The solution was pipetted into a flask con-
taining a known amount of n-octane. The resulting solution
was immediately analyzed and used.
Preparation of Pure and Base-added sec-Butyllithium Solutions
Reagents
sec-Butyllithium, pure liii'hium phenoxide Lithium ethoxide Lithium sec-butoxide n-Octane, 99 mole per cent minimum purity, redistilled n-Pentane, 99 mole per cent minimum purity, redistilled T,2-Dibromoethane, reagent grade
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23
Procedure
The n-octane and n-pentane stored in the dry "box were
distilled from, lithium aluminum hydride to insure dryness.
The solutions of sec-butyllithium were analyzed by the
method of Oilman and Cartledge (1) using 1,2-dibromoethane.
n-Pentane was used as the solvent for the analysis instead
of ether since sec-butyllithium cleaves ether at a very
rapid rate. Analysis of dilute solutions using both methods
gave excellent agreement.
About five grams of the desired alkoxide was placed in
a 125 milliliter Erlenmeyer flask which contained about 30
milliliters of a pure sec-butyllithium solution, usually
0.8 N in sec-butyllithium. The flask was securely stoppered
and brought out of the dry box. The flask was placed in a
mechanical shaker and shaken for the required number of days
dependent upon the alkoxide being used (five days for lithium
sec-butoxide and phenoxide and one day for lithium ethoxide).
The resulting solution was yellow to red in color. The flask
was taken back into the dry box and the solution filtered
and analyzed.
A solution of the desired concentrations in base and
sec-butyllithium was prepared by mixing appropriate quantities
of analyzed solutions of pure sec-butyllithium in n-octane and
based-added sec-butyllithium in n-octane with the necessary
quantity of n-octane. The resulting solution was reanalyzed
to insure concentrations of sec-butyllithium and base.
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24
Thermal Decomposition of sec-Butyllithium Solutions
Reagents
Analyzed solution of sec-butyllithium and lithium alkoxide
Procedure
Twenty milliliters of the analyzed sec-butyllithium
solution was pipetted into the decomposition vessel shown
in Figure 4, page 20. The vessel was stoppered with a vacuum
stopcock adapter, brought out of the dry box, and fitted
onto the vacuum line. The lower part of the vessel which
contains the solution was submerged in a Dewar of liquid
nitrogen. After the solution was completely frozen the
vessel was evacuated and the entire system flushed three or
four times with argon gas introduced into the system through
the gas port tube, Figure 5, page 21. After the last flush-
ing a residual pressure of 25 centimeters of argon gas was
retained and the system cut off from the vacuum pump. The
Dewar of liquid nitrogen was removed and the solution warmed
to room temperature. While the solution was warming a stir-
ring motor fitted with a horseshoe magnet was positioned
above the bar magnet of the decomposition vessel and the
condenser of the decomposition vessel was connected to a
circulating water reservoir regulating at 31.0° i 0.5°C.
After the solution v/as completely warmed to room tem-
perature, stirring was started and the manometer pressure
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25
was recorded, using a cathetometer accurate -to £0.1
millimeter. The barometric pressure was recorded. A
regulating water-ethylene glycol bath (about a 1:1 mixture)
previously set at 94.10° db 0.05°C was raised around the
entire lower end of the decomposition vessel. Simultaneously
a timer, reading seconds to sec., was started. Manometer
pressures and barometer pressures were recorded at various
time intervals. During the initial moments of the decom-
position data were recorded as often as possible. After the
gas evolution had leveled off data were recorded every 0.25
or 0.50 centimeter of pressure until the reaction appeared
to stop.
After the reaction appeared to stop the vacuum stopcock
adapter connecting the decomposition vessel to the vacuum
line was closed and the hot water-ethylene glycol bath was
lowered. The gases were subsequently analyzed on a gas
chromatograph.
A plot of the total corrected pressure versus time was
made and in all cases found to conform to the general shape
of the curve shown in Figure 6, page 26.
The rapid initial rise was found to be primarily due
to the solvent coming to equilibrium at the condenser
temperature^ and in all runs the slope and height of the
initial rise were approximately the same.
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26
t P
(cm. Hg)
t (hr.)
Pig. 6—A typical pressure versus time plot for de-composition gases.
The data points falling in the straight line region of
the graph shown in Figure 6 were utilized in a least-squares
curve fit to determine the equation of the straight line.
The intercept value (t = 0) was taken as the pressure change
due to the n-octane solvent vapor and subtracted from the
above data points to obtain the pressure increase due to the
olefin gases.
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27
The pressure due to the olefin gases, P(olefin), was
utilized in the following equation
+ [p.* - P(olefin)] = kt + C [4]
where t is the time in hours and C is an integration constant.
The pressure at infinite time, P*, , was calculated in the
following manner
So = (Vl)(RLi)RT/ (Vg) [5)
where VI is the volume of the liquid phase, HLi is the gross
initial alkyllithium concentration, T is the absolute tem-
perature of the gases, R is the international gas constant,
and Vg is the volume occupied by the gases. Agreement between
the calculated pressure at infinite time and the observed
pressure at infinite time was excellent,as seen in Table II.
TAB IE II
DIFFERENCES IN P^ OBSERVED AND CALCULATED
RLi (moles/ liter)
P.*, Observed (cm./ Hg)
Poo Calculated" (cm./ Hg)
0.381* 18.24 18.80 0.381* 20.99 20.96 0.239 11.81 11.80 0.502 25.25 24.78 0.208 9.48 10.27
*Two different decomposition vessels were used and the P^ difference is a reflection of the difference in their respective volumes.
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28
A graph, of +§?<» - P( olefin J2" versus time was con-
structed and, with the exception of a few points near time
equal zero, was found to be linear. Least-square analysis
of the data was used to evaluate k and C in equation 4.
Analysis of Gaseous Products
Reagents
Product gases from the thermal decomposition
Procedure
The gases were identified on a Wilkins Aerograph gas
chromatograph using a 20 feet by % inch column packed with
20 per cent didecylphthalate substrate on Chromosorb-P treated
with hexamethyldisilazane. A filament current of 200 milliamps
was used. Column temperature was maintained at 40°C and the
detector oven was maintained at 200°C. Helium carrier gas
flowed at a rate of 49.1 milliliters per minute. The re-
corded peaks were identified by comparison of retention times
with known standards (3). Relative volume per cents were
determined by the method of peak height times the width at
half peak height.
Gas samples were obtained by two methods. In one method
a 1/8 inch diameter copper tube was connected directly from
the gas port tube of the vacuum line to a one milliliter gas
sample loop on the chromatograph and the gases were sampled
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29
directly from the vacuum line. In a second method the
gases were condensed in a trap with liquid nitrogen and
transferred to a vacuum line in series with the chromato-
graph and then sampled with the gas loop. Both methods
yielded the same results. Figure 7, page 30, shows a
typical chromatogram. The unidentified peak has "been shown
to "be n-pentane, the solvent used in the preparation of
both the sec-"butyllithium and the lithium sec-but oxide.
Product Distribution Versus Time
Reagents
sec-Butyllithium, pure Analyzed solution of sec-butyllithium and lithium alkoxide
Procedure
A pure sec-butyllithium sample was treated as before (3,
p. 13) and the relative product distribution versus time was
determined. The pure sec-butyllithium was pyrolyzed at 104°C.
The rate constant for the pyrolysis is 27.52 ±2.05 sec"*-*- (4,
p. 21) therefore pyrolysis proceeded with a half-life of
2518 seconds. The sample was decomposed for 4.8 half-lives.
At intervals of about 800 seconds a chromatograph injection
of the product gases was made, with the first injection made
416 seconds after decomposition was started. It was found
that the relative product distribution remained constant with
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30
St.
RUN 26
0.373 M sec-Butyllithiuia
0.391 M lithium sec~Butoxide
I air
II 53# 1-Butene
III 26$ trans-2-Butene
IV 21# cis-2-Butene
II III IV
Fig. 7—Gas chromatogram of pyrolysis gases
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31
G EI © o *
c\j
0 T3 •H X s O
. £5 P 3 •p s •H 0 H 0) rH ca >s P 3 2
•H O -p 0) •H CO
vo ' s vo ' C\j frA H fei tA fA b •
p$ 0 O
D
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0 d 0 0 -p CS
0 PQ •p
CD f a c\j m 0 f 1 p CD CM
a 1 PQ 05 CO I u »H
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0 ©
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0 ©
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tn « rH
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IA «
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o o ts~\
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0 J p 0) 3 03 Jh 0) >
c o •H •P rQ •HI 43 CO *H nd 43 O 3 O
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f GO h0 •H
Relative per cent (^)
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32
time at the values of 36.1 per cent 1-butene, 19.0 per cent
trans-2-butene, and 44.8 per cent cis-2-butene. A total of
sixteen samples .was-; analyzed.
Two analyzed solutions of sec-butyllithium and lithium
sec-butoxide were treated as if for thermal decomposition.
The kinetics. of the decomposition was not determined, but
rather the product distribution versus time was determined.
The same method of gas analysis was used as discussed in
the analysis of gaseous products section in this chapter.
The results of one of these determinations is shown graph-
ically in Figure 8, page 31. In both cases the relative
per cent of 1—butene initially drops, the relative per cent
of trans—2—butene initially increases, and the relative per
cent of cis-2-butene remains constant. The final relative
values in both cases correspond to the product distribution
observed when lithium sec-butoxide was used to catalyze the
thermal decompositions from which kinetic data were obtained.
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CHAPTER BIBLIOGRAPHY
1. Gilman, H. and P. K. Oartledge, "The Analysis of Organo-lithium Compounds," Journal of Organometallic Chemistry, II (1964), 447.
2. Glaze, Yfilliam H., Jacob Lin, and S. G. Felton, "The Thermal Decomposition of sec-Butyllithium," Journal of Organic Chemistry, XXX (1955"), 1258.
3. Kamienski, C. W. and D. L. Esmay, "Effect of Sodium in the Preparation of Organolithium Compounds," Journal of Organic Chemistry, XXV (I960), 1870.
4. Lin, Jacob, "Thermal Decomposition of Alkyllithium Com-• pounds in the Pure State," unpublished master's thesis, Department of Chemistry, North Texas State University, Denton, Texas, 1965.
33
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CHiLPTER III
RESU1TS AND DISCUSSION
It has "been reported by Brown and his co-workers (2)
that the ethyllithium hexamer does not disassociate upon
reaction with lithium ethoxide, hut rather a complex re-
sults in which an alkoxide moiety is complexed onto one or
both of the open faces of the octahedral hexamer. The same
results were noted with triethylamine (l) except at high
base to alkyllithium ratios, where the hexamer disassociates
to form complexed dimers. On the other hand, it has been
shown that the tert-butyllithium tetramer, which does not
have open faces, must disassociate before complexation with
triethylamine can occur (4).
Kutta (6) has shown that the pyrolysis of n-butyllithium
solutions is catalyzed by lithium n-butoxide, and that the re-
action is first order in alkyllithium for all of the isomeric
butyllithiums except sec-butyllithium. In this work, the
pyrolysis of the sec-butyllithium tetramer* in n-octane was
found to be catalyzed by various lithium alkoxides. The
distribution of olefin products, 1-butene, trans-2-butene,
and cis-2-butene, does not appear to result from a stereospecific
^Preliminary studies indicate that sec-butyllithium exists as a tetramer in hydrocarbon solution at room temperature.
34
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35
elimination as has been reported for the unsolvated pyrolysis
of the same compound (5).
The observed elimination to produce the olefins and
lithium hydride could proceed by one of the following
mechanisms. (RLi refers to sec-butyllithium, B refers to
lithium alkoxide or other bases.)
Mechanism 1.
(RLi)4 - B (RLi)4 B
(RLi)^ B "sVQW>- olefin + LiH + (RLi)5 B-
d [olefin] /dt = k [(RLi)4 B]
= kK[(RLi)4] [B]
= k' [(RLi)4]
Mechanism 2.
§(RLi)4 - B (RLi)2 B
B -TEST OLEFIN *LIH + ,RAI B
d [olefin] /dt=k [(RLi)2 b]
— kK [(RLi) 4 ^ [B]
=K> [(SIi)4JS
Mechanism 3.
i(Eii) • B (RLi) B
(KM.) B olefin * liH * B
d [olefin! /dt=k [(KLi) b J
=KK [(RLi)4]? [B]
=&• [(Eli)4]i
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36
Mechanism 1 results in the following pressure relation-
ship (see Appendix B):
+log(Pao - P) = kobst - C
where P is the pressure at infinite time, P is the pressure
due to the olefin gases at any time t, k^g is the observed
rate constant, and C is an integration constant. A plot of
the above function was not linear, indicating that the data
do not fit this mechanism.
Mechanism 3 results in the following pressure relation-
ship (see Appendix B):
+ (Poo " ?)3/4 = kobst + C.
A plot of this function was not linear, indicating that the
data do not fit this mechanism.
Mechanism 2 results in the following pressure relation-
ship (see Appendix B):
+ (P„ - P)* = kobst + C.
As shown in Appendix A, the observed data fit this relation-
ship, suggesting that mechanism 2 is operative in this pyrolysis,
Summarized in Table III are the results of the pyrolysis
data obtained in this work. The rate constants, k0-bs, were
obtained as- slopes from plots of +(P<0 - P)¥ versus time
(see Table III, page 37). The results summarized are those
in which the dimer to base ratio is greater than one. At
lower dimer to base ratios, complexation by more than one base
species may occur and mechanism 2 may not be the only mode of
decomposition.
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37
TAB IE III*
PYROLYSIS** OF sec-BUT YLLITHIUM SOLUTIONS
Run No.
(sec-BuLi) (moles/liter)
s-BuOLi (moles/liter)
• ohs (cmHg)'£*/hr
31 0.330 0.124 2.743 41 0.350 0.081 2.193 38 0.235 0.076 1.894 7 • 0.381 0.064 1.000 40 0.356 0.063 1.757 30 0.313 0.061 1.684 12 0.381 0.044 1.141 32 0.391 0.042 0.635 36 0.351 0.037 0.683 37 0.201 0.036 0.663 35 0.208 0.033 0.602 34 0.374 0.029 0.747
Li 00
17 0.338 0.074 3.102 15 0.320 0.068 2.672
LiOEt
20 0.242 0.081 3.250 21 0.502 0.097 2.833
*See Appendix A for individual runs -
**Pyrolysis temperature is 94.10 - 0.05°C
To determine the kinetic order of the "base catalyst the
following relationships were used:
k ohs k B n
log (kobs) = l0& K + n log B
Blog (kote) = n 3 (log B)
31og (k0-bs)/'dlog B = n
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38
A plot of log (^obs) versus log B was made (see Figure 9,
page 39) using the data for lithium sec-"but oxide summarized
in Table III, page 37. The data were subjected to least-
squares analysis and found to have a slope of 1.16 ± 0.11.
The slope determined is the kinetic order, n of the base
catalyst. Deviations in are probably due to the
presence of a higher base concentration than determined by
analysis- The higher base concentration arises from a re-
action of sec-butyllithium with trace impurities of water
and oxygen trapped in the decomposition vessel while the de-
composition solution was being prepared in the dry box or
handled on the vacuum line (see Chapter II, p. 24). The re-
actions would produce lithium sec-butoxide and lithium oxide.
These species would increase the base concentration and make
kobs appear too large for the analyzed base concentrations.
The data summarized in Table III, page 37, indicate that
the catalytic effect of the bases used is in the order
Lithium ethoxide (LiOEt)^.
Lithium phenoxide (Li0jZf))>
Lithium sec-butoxide (s-BuOLi)
However, it is felt there are not sufficient data to determine
an exact relationship between the catalysts, since only a few
runs were made with LiOEt and L1O0. Furthermore, it is pos-
sible that the s-BuOLi is present as an impurity in all runs.
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39
©
©
* ©
® *
©
©
* G * ©
o C\J * o
7H ' 6 «.• *
o o
l°g(kobs)
w v«-> 0 o
© rH © /-N CD O rH o
CO •p r> Lf\ •H H o •
P4 H rd + 0) -p 05 o> H KN 3 H o . »
H O 03 il O cr>
CD CO rA -P 0) Lf\ JH *
*r-4 H o p« O4 II m 1—1 05 •p CO
CO 05 o o CD ccJ H V—•'
0 * tlO o
o I
—t— CM o I
in * rH f
s H 1 o
H CO CD JH m 0
»W> > *-n o CO
tr\ H rQ % O H
CVJ rH i
rH I
0 O H <H O
P< 05 in es i r cr>
W •H
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40
More data must be obtained before a complete discussion of
the base effect is possible.
The product distribution observed in the pyrolysis
remained constant as the concentration of lithium sec-
butoxide was changed, as shown in Table IV. It was also
found that the product distributions observed when the other
two alkoxides were used as catalysts remained constant.
TAB IE IV
AVERAGE PRODUCT DISTRIBUTION VERSUS THE AIKOXIDE MOIETY*
Alkoxide fo fo trans-2 c/> cis-2 1-Butene Alkoxide 1-Butene Butene Butene 2-Butene
Lithium ethoxide 72.6*1.9 15.5*1.3 11.9*0.4 2.65
Lithium phenoxide 63.443.6 18.2*1.1 17.8*2.0 1.76
Lithium sec-butoxide 51.4*4.4 27.3-3.1 21.3-1.2 1.06
*See Appendix A for values of individual runs
By comparing the observed product distribution to the
product distribution obtained from other sec-butyl systems,
Table V, it can easily be seen that a cis-elimination pathway
is suggested.
The cis-elimination mechanism assumes a cyclic transition
state in which the^-hydrogen is eliminated while in the cis-
position with respect to the other leaving group.
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41
TABLE V
DLIMIHATIOU REACTION PRODUCT DISTRIBUTION FOR sec-BUTYL SYSTEMS (3)
Substituent 1-Butene c/o trans~2 # cis-2'""
BuWne Probable Mechanism
-(CH 3) 2H -O~ 67 21 12 cis
-OCOCH3 57 28 15 cis
-OCSSCH3 42 40 18 cis
- M 2 , M O 2 25 56 19 trans
-Br, C2H5O 20 59 21 trans
-OTs 10 47 43 E I
The observed pyrolysis products, olefin and lithium
hydride, could be produced from somewhat ionic or polar
transition states as represented in Figure 10, and Figure 11,
page 42.
H 3CH 2O. .Li
hct- ^;CH
' E0C v. ~Li H r-
•CH-
Fig. 10—Possible transition state leading to 1-butene
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42
Li ^ C H 2 C H 3
HC*-- CH
CH^-HC^ Li CH3
H s-
Pig. 11—Possible transition state leading to 2-butene
Addition of alkoxide to either of the transition states
shown in Pigures 10 and 11 would serve to stabilize the
ionic nature of the transition state, and result in an in-
crease of olefin character. The overall result would be to
stabilize the polar transition state in the non-polar solvent.
Due to its intimate association in the transition state,
the alkoxide would be expected to influence both the rate of
pyrolysis, as has already been shown, and the observed product
distribution. As the basicity of the alkoxides increases the
transition state shown in Pigure 11 would become more stable
and an increase in the amount of 2-olefin or a decrease in
the l-olefin/2-olefin ratio would be expected. The relative
basicities of the alkoxide used in this study should be in
the following order of decreasing strengths:
s-BuOIi > LiOEt > TiiO0
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43
As seen in Table IV, page 40, when lithium sec-butoxide is
used as the catalyst more 2-olefin is produced; however,
the relative amounts of 2-olefin are lower for lithium
ethoxide than for the phenoxide case. This is in reverse
order to that expected. The relative steric volumes of
the alkoxides should follow the trend;
s-BuOii > LiOEt, s-BuOLi > LiO0
and it would be expected that as the steric volume increases
the relative amounts of 1-butene should increase. As seen
in Table IV, page 40, this is contrary to the observed trend.
It is also possible that the orientation of the complexed
dimer accounts for the observed product distribution. However,
our knowledge of the geometry of the complex is insufficient
to produce accurate models to evaluate this possibility.
Additionally, the elimination may proceed through an
assisted pathway in which the lithium ion of the alkoxide
ion pair becomes associated with the leaving hydride ion.
Further experiments are suggested in which other metal
alkoxides (such as sodium) and neutral bases are used as
pyrolysis catalysts.
The suggested mechanism, mechanism 2, does not take into
account possible decomposition of the uncomplexed tetramer.
However, this process would be expected to have a higher
activation energy than that proposed by mechanism 2. The
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44
preparation of base free solutions of sec-butyllithium is
very difficult and has not been accomplished at the time
of this writing.
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CHAPTER BIBLIOGRAPHY
1. Brown, Theodore I., R. L. Gertesis, D. A. Bafus, and J. A. ladd, "Interaction of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Triethylamine in Benzene," Journal of the Ameri-can Chemical Society, LXXXVI (1964), 2l55.
2. Brown, Theodore I., J. A. ladd, and G. N. Newman, "Inter-action of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Lithium Ethoxide in Hydrocarbon," Journal of Organometallic Chemistry, III (I965), 1.
3. De Puy, C. H. and R. V/. King. "Pyrolytic Cis Eliminations," Chemical Reviews, LX (i960;, 431.
4. Eastham, Jerome P., Prank A. Settle, and Maureen Haggerty, "High Frequency Titrimetric Determination of the Electron Deficiency in Lithium Alkyls," Journal of the American Chemical Society, LXXXVI (1964), 2076.
5. Glaze, William H., Jacob Lin, and E. G. Pelton, "The Thermal Decomposition of sec-Butyllithium," Journal of Organic Chemistry, XXX (19^5), 1258.
6. Kutta, H. W., "The Pyrolysis of Alkyllithium Compounds in Solution," unpublished master's thesis, Department of Chemistry, Ohio State University, Columbus, Ohio, 1964.
45
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APPENDIX A
rH w H W YA &
of 0 wl
r~i 00 00
P3 ft M X o H P *? O 0 ca
M s EH Hi h3
J-vO O
O lr\ o irv
(Xj
0 1 « CM
tt\
H
lr\ • • O
ri\O OJ • • • CMlLnoj ITxOJ CM
•p o 0) o o 0 0 • •p c H « 3 0 i
o cq -p i • *H 0 I p
-P C C\J PQ H L rQ ^ 0 1 s O W ,jQ *P W CM Jh ^ -H ^ a 1 • O -P JL| pQ CD* M
J" . * *P 1 £~j •H H co H P O u •H rd i—i -p
o a £ •H o 0 H p O Pn 1 -
J* ro no CM
V (?H *™) %[(«TJ©I0)d -°*d]
^6
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M K
s o
3.5-
3.0-
•H S 2-5H 0 Ph 1
A 2.0-1
*+7
HUN 12
0.381 M sec-BITTYLLITHIUM
0.0M+ M LITHIUM sec-BUTOXIDE
[P..- P ( o l e f i n ) ] * = ^.836 - 1.1^-1 t
1 . 5 2.0 t (h r . )
Product d i s t r i b u t i o n :
% 1-Butene 50*7% 1° t rans-2-Butene 28.2% % cis-2-Butene 21.1$
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3.5-
uo w 3.0-
s o
32.5 •H Ch 0 H 0
^ 2.0' 1 Of
kQ
RUN 15
0.320 M sec-BUTYLLITHIUM
0.068 M LITHIUM PHENOXIDE
[P^- P(olefin) = .216 - 2.672 t
0.5 1.0 t (hr.)
Product distribution:
% 1-Butene 59 ?7f° % trans-2-Butene 19®3% % cis-2-Butene 19«9%
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H-9
3.5'
m 3.0' w
a o
Ci •H CH 0) H O K
n?
2.5'
2.0-
1.5-
RUN 17
0.338 M sec-BUTYLLITHIUM
0.07^ M LITHIUM PHENOXIDE
[P - P(olefin) ]'* = .370 - 3.102 t
0.? t (hr.)
1.0
Product distribution:
% 1-Butene % trans-2-Butene % cis.-2-Butene
67.0^ 17*1% 15.8 %
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50
3.5-
h0 w
a 3-0-O
2.5-c •H
CD H O
^ 2.0-i
P-? 8
RUN 18
0.239 M sec"BUTYLLITHIUM
0.283 M LITHIUM ETHOXIDE
[P^- P(olefin)]* = 3A9^ - 3.637 t
-T 1 r 0.1
t (hr.) 0.3
1 r 0 . 5
Product distribution:
% 1-Butene % trans-2-Butene 1° cis-2-Butene
71. 16. 11.9#
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51
a o
•H 4-i CD rH O P*
w
3.0
2.5-
2.0
RUN 19
0.235 M sec-BUTYLLITHIUM
0.173 M LITHIUM ETHOXIDE
[P^- P(olefin)] = 3A87 - 3.039 t
0.2 0.5 t (hr.)
Product distribution:
% 1-Butene 75»5% % trans-2-Butene 13.6$ % cis-2-Butene 11.3$
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52
txO W
o
E5 •ri
0 r~i O CU
3.0
2.5-
2.0
J 1.5-
RUN 20
0.2ll-2 M sec-BUTYLLITHIUM
0.081 M LITHIUM ETHOXIDE
[P„- P(olefin) ~fz = 3.953 - 3.250 t
0.3 0.6 t (Jar.)
0.9
Product distribution:
% 1-Butene 71*1$ 1° trans-2-Butene 16.2$ $ cis-2-Butene 12.6$
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53
* bQ w
O
•H ©
0 v a. 1 oJ*
^.0
3.5
3.0-
2.5-
2.0-
RUN 21
0.502 M sec-BUTYLLITHIUM
0.097 M LITHIUM EIHOXIDE
[P^- P(olefin) ] = 5-657 - 2.833 t
0.5 1.0 t (hr.)
l.*f
Product distribution:
% 1-Butene 6 0.7% % trans-2-Butene 21.2$ % cis-2-Butene 18.1$
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5k
5.0-
3 k.5-
a o
T-. £ •H <D H 0 -w Oh 1 0$
+.0
3.5-
3.0 -
RUN 22
0.695 M sec-BUTYLLITHIUM
0,b$2 M LITHIUM sec-BUTOXIDE
[P„- P( olefin)]2" = 6.502 - 8.372 t
0.15 0.3 0.5 t (hr.)
Product distribution:
% 1-Butene *+8.3$ % trans-2-Butene 29-3$ % cis-2-Butene 22.h%
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55
&0 W
a o
s •H <m 0 H 0 K 1 p}
3.0
2.5
2.0
RUN 30
0.313 M sec-BUTYLLITHIUM
0.061 M LITHIUM sec-BUTOXIDE
[P.O- P(olefin)]4 = .232 - 1.68J+ t
0.6 1.0 t (hr.)
1.5
Product distribution:
% 1-Butene k-8.2% 1° trans-2-Butene 29• 2% % cis-2-Butene 22.5$
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56
txO w
o
ci •H <d H 0 v-/ Ph 1 p*
3.5'
3.0
2.5
HUN 31
0-330 M sec-BUTYLLITHIDM
0.12>+ M LITHIUM sec-BUTOXIDE
[P„- P(olefin) ] = *k532 - 2.7^8 t
0:5 ' 1.0 t (hr.)
Product distribution:
fa 1-Butene , k6.1% % trans-2-Butene 31.8% % cis-2-Butene 22.0%
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57
CM no
O «
.p tf\ OQ \D
a?
• ""r ir\
• oo O m
lr\ CM
H
C\i
\D CM CO • • • OOCO no j1 CM CM
o * 0 o £
I o a> CD • • 0 43 a o "cm a 2 0) ON •"~N o CQ-p lf\ m •H 0 1 P • .p C CM CQ J* £ 0 I i w ,o -P W [CM 11 •H 2 £j t
* -p fn m co \vA I—i
•P 1 u I—i CO r-i -P Of •~N •H a * r$
*H 43 0) H O 3 O rd 0 OH Irs • « ' u
^SH -rao) [(UTjeio)d: -~d]
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58
0-w a o 3.5-
«ri <H <D o3*0-
v-y
PLi
I 0$ •—'2.5-
HUN 3^
0.37^ M sec-BUTYLLITHIDM
0.029 M LITHIUM sec-BUTOXIDE
[P«- P(olefin) ] 1 = if.869 - 0.7^7 t 1:6 " ' ' 2T0 ' ' — 2 7 3 ^
t (hr.)
Product distribution: % 1-Butene 1+9. % trans-2-Butene 28. % cis-2-Butene 21.
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59
w Q J—4 IS x; o r<
M « « . EH i M a }~3 0
In
to
m W i w Of EH 0 M ml »-3
S s s
rO 00 oo o ro CM O
& • •
PS o o
*p
CM O vD •
O
I
CO CM m • no
ii
i—i
3
0 H 0
01
w
o cm
lT\ » •
H
o ' • H
lr\ •
O
Jr CM 00 • • • CO O H Jr no CM
a 0 •H •P
•H 14 •P ia
*d •p
o
£ o J4 Oh
0 c 0 0 •p a 2 0 m +3
0 i 3 .0 CM PQ 0 I 1 «P so CM
1 W CD 10 * $H •H H -p O
O
ro
lr\
CM
O
CM
^(Sn - m o ) ^ [ ( U f j e t o j d - ~ j ]
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60
« H XI
*«r~» O
M PD W m CH i W o t
0)
l
£01
m M i ffl a H a) W to
S s \ D no H EN.
u \ n o S no O p • •
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no n o \0 m 0 1
en H vO •
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et o •H •P
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P
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IN-O CM nOCvJ
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- p £ 2 Q) PQ+>
CD I £ a CM pq a) i i
CM I w
•H | O
-P w £ s «?£ rH -P
, ( S H - r a o ) [ ( U T J 0 i o ) d - ~ d ] A A
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61
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"cm
:h ; o
+3 to 2 g
pq «i l h
H -P
( § H -TOO) [ ( U i j e i o ) d - ° a ]
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M
a o
•H Q) r4 O •w Oh
p!
3.0 -
2.5
2.0
1.5-
62
RUN 38
0.235 M sec-BUTYLLITHIUM
0.076 M LITHIUM sec-BPTOXIDE
[P^- P(olefin)]2 = 3.571 - 1.89^ t
0.5 1.0 t (hr.)
Product distribution:
% 1-Butene 1° trans-2-Butene 1° cis-2-Butene
63.7%
Vo.%
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63
bO
a o
»S» I—I •H «H <D H 0 eC 1 o?
3.5-
3.0-
2.?.
2.0
RUN ^0
0.356 M sec-BUTYLLITHIUM
0.063 M LITHIUM sec-BUTOXIDE
[P^- P(olefin) ] = - 1.757 t
0'.5 1.0 t (hr.)
T7¥
Product distribution:
% 1-Butene 60.8$ % trans-2-Butene 20.5$ % cis-2-Butene 18.7$
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6b
*bQ W
•H CH 0
H O
V-/ PH
p?
3-5
o 3.0
2.5'
2.0
RUN lj-1
0.350 M sec-BUTYLLITHIUM
0.081 M LITHIUM sec-BUTOXIDE
[Pw- P(olefin)]4 = - 2.193 t
0.5 1.0 t (hr.)
Product distribution:
% 1-Butene 60.0$ % trans-2-Butene 22.2$ % cis-2-Butene 17.8$
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APPENDIX B
RLi = sec-Butyllithium
B — Base
n[(RLi? t = ntaliJJ. - n« RLi^ a e o o m p o s e a
= nf(RLi^30 - nColefin)^
= nColefin , - *+n( olefin)
n = number of moles 0 = initial amount
t = amount at time t
[olefin] = n(olefin)/VI [ ] = concentration VI = volume of liquid
phase P(olefin) = k X(olefin) k = Henry's Law
£ ku[olefin] constant X = mole fraction
[olefin] = n(olefin)/VI = P(olefin)/k"
(1/k") [d.P(olefin)/dt] = d[olefin]/dt
[ (RLi) j ] = (VDCnCRLi)^]
(Vl)[(RLi)If]t = (Vl)(l/k")[P» - P( olefin) ]
[(RLi)lf]t = ( V k » ) I X - P(olefin) ]
From Mechanism 1, page 35*
d[olefin]/dt = k'CCRLi)^] k' = kK[B]
substituting from the above relationships
(1/k") [dP(olefin)/dt] = (k1) ( /k51) [P«-P(olefin) ]
65
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66
JdP(olefin)/IX- P(olef in)] = ^k'jdt
log [R.- P(olefin)] = kQbs t + C
For Mechanism 2, page 35*
d[olefin]/dt = k« [(RLi) f2- k* = KK[B]
which on substitution yields
(l/ku)[dP(olefin)/dt] = 2k'(l/kn)^[P^- P(olefin)]
JdP(olefin)/[Ro - P( olefin) ]/z = 2k' (l/k^Jdt
-2[P - P(olefin)]'4 = 2k1 (k") t + C
[P - P(olefin)]'4 = k . t + C obs
For Mechanism 3, page 35»
d [ o l e f i n ] / d t = k1[(RLi)^]^ k1 = kK[B]
reduces as in the above case to
JcLP(olefin)/[£«,- P(olefin)]* = k1 (Vk")*Jdt
which yields on integration
[P - P( olefin) ]^ = k t + C
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BIBLIOGRAPHY
Books
Coates, G. E., Organo-Metallic Compounds, New York, John Wiley and Sons, Ino., 1956.
Articles
Berkowitz, Joseph, D. A. Bafus, and Theodore L. Brown, "The Mass Spectrum of Ethyllithium Vapor," Journal of Physical Chemistry, LXV (1961), 1380.
Brown, Theodore L., D. W. Dickerhoof, and D. A. Bafus, "The Infrared and Nuclear Magnetic Resonance Spectra of Ethyl-lithium," Journal of the American Chemical Society, IXXXIV (1962), 137X7
Brown, Theodore L., R. L. Gerteis, D. A. Bafus, and J. A. ladd, "Interaction of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Triethylamine in Benzene," Journal of the American Chemical Society, LXXXVI (1964), 2135.
Brown, Theodore L., J. A. ladd, and G. N. Newman, "Interaction of Alkyllithium Compounds With Base. Complex Formation Between Ethyllithium and Lithium Ethoxide in Hydro-carbon," Journal of Organometallic Chemistry, III (1965), 1.
Bryce-Smith, D., "Organometallic Compounds of the Alkali Metals. Part V. The Non-Radical Decomposition of n-Butyllithium," Journal of the Chemical Society (1955), 1712.
Cheema, Zafarullah K., G. W. Gibson, and J. P. Eastham, "The Structure of Butyllithium in Ether: A Solvated Dimer," Journal of the American Chemical Society, LXXXV (1963), 3517-35197
De Puy, C. H., and R. W. King, "Pyrolytic Cis Eliminations," Chemical Reviews, IX (i960), 431.
Dietrich, H., "Die Kristallstruktur von Athyl-Lithium," Acta Cr.ystallographica, XVI (1963), 681.
67
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68
Eastham, Jerome P., Prank A. Settle, and Maureen Haggerty, "High Frequency Titrimetric Determination of the Electron Deficiency in. lithium Alkyls," Journal of the American Chemical Society, LXXXVI (1%4), 2qTo.
Glaze, William H., Jacob lin, and E. G. Pelton, "The Thermal Decomposition of sec-Butyllithium," Journal of Organic Chemistry, XXX (1965), 1258.
Gilman, H. and P. K. Cartledge, "The Analysis of Organo-lithium Compounds," Journal of Organometallic Chemistry. II (1964), 447.
Kamienski, C. W. and D. L. Esmay, "Effect of Sodium in the Preparation of Organolithium Compounds," Journal of Organic Chemistry, XXV" (i960), 1870.
Margerison, D. and J. P. Newport, "Degree of Association of n-Butyllithium in Hydrocarbon Media," Transactions of the Parada.y Society, LIX (1963), 2058.
Rodionov, A. N., D. N. Shigorin, and T. V. Talalaeva, "A Study of the Structure of Complex Aliphatic Organic Lithium Compounds," Doklady Akademii Nauk, English translation, CXXXXIII (l5'6$),' "173'.
Rogers, M. T. and A. Young, "The Electric Moment of n-Butyllithium and the Nature of the Lithium-Carbon Bond," Journal of the American Chemical Society, LXVII (1946),
Rundle, R. E., "Electron Deficient Compounds," Journal of Physical Chemistry, LXI (1957), 45.
Schlenk, W. and J. Holtz, "IJber die einfachsten Metall-organischen Alkiliverbindungen," Berichte Per Deutschen Chemischen Gesellschaft, L (1917), 2b£>.
Schorigin, P., "Uber die Natriumalkyle und ihre Reaktion Mit den Atheru," Berichte Der Deutschen Chemischen Gesellschaft, XXXXIII (191377 1931.
Thompson, T. and T. S. Stevens, "Organic Compounds of Boron," Journal of the Chemical Society (1933), 556.
Vfeiner, Michael, George Vogel, and Robert West, "The Physical Properties and Structure of t-Butyllithium," Inorganic Chemistry, I (1962), 654.
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69
Weiss, E. and E. A. C. Lucken, "Die Kristall- und Elektronen-struktur des MethyllithiumsJournal of Organometallic Chemistry, II (1964), 197. "
Wittig, G., P. J. Meyer, and G. Lange, "Uber das Verhalten von Diphenylmetallin als Komplexbildner." Justus Liebigs Annalen der Chernie, DLXXI (1951;, l'b'7.
Ziegler, K. and H. G. Gellert, "The Thermal Stability of Lithium AlkyIs," Annales de Chimie, DLXVII (1950), 179*
Unpublished Materials
Kutta, H. W., "The Pyrolysis of Alkyllithium Compounds in Solution," unpublished master's thesis, Department of Chemistry, Ohio State University, Columbus, Ohio, 1964.
Lin, Jacob, "Thermal Decomposition of Alkyllithium Compounds in the Pure State," unpublished master's thesis, Depart-ment of Chemistry, North Texas State University, Denton, Texas, 1965.
Morton, Maurice, L. J. Fetters, and R. A. Pett, "Association of Organolithium Macromolecules," unpublished paper read before the Second International Symposium on Organo-metallic Chemistry, Madison, Wisconsin, August 50, 1965.