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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

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

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

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

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

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

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

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.

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.

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).

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

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

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.

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.

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

12

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.

13

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.

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

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

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

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

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

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

20

Pig. 3—Distillation vessel

Pig. 4—Decomposition vessel

<0 CO 3 <£ CD

21

a 0

CD

CO

3 0 03

1 IA

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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

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.

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

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.

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.

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.

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

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

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

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

©

O

O

O

©

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

1—i •p O

o • o

0 ©

a ©

El ©

EI ©

0 ©

• ©

tn « rH

o • p H

IA «

O

O KO

o LA

o o ts~\

o CM

0 J p 0) 3 03 Jh 0) >

c o •H •P rQ •HI 43 CO *H nd 43 O 3 O

u

f GO h0 •H

Relative per cent (^)

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.


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

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

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

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.



+ (Poo " ?)3/4 = kobst + C.

A plot of this function was not linear, indicating that the

data do not fit this mechanism.



+ (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.

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

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.

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

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.

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

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

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

44

preparation of base free solutions of sec-butyllithium is

very difficult and has not been accomplished at the time

of this writing.


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

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

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$

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%

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


0.07^ M LITHIUM PHENOXIDE

[P - P(olefin) ]'* = .370 - 3.102 t

0.? t (hr.)

1.0


% 1-Butene % trans-2-Butene % cis.-2-Butene

67.0^ 17*1% 15.8 %

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


% 1-Butene % trans-2-Butene 1° cis-2-Butene

71. 16. 11.9#

51

a o

•H 4-i CD rH O P*

w

3.0

2.5-

2.0

RUN 19



[P^- P(olefin)] = 3A87 - 3.039 t

0.2 0.5 t (hr.)


% 1-Butene 75»5% % trans-2-Butene 13.6$ % cis-2-Butene 11.3$

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


[P„- P(olefin) ~fz = 3.953 - 3.250 t

0.3 0.6 t (Jar.)

0.9


% 1-Butene 71*1$ 1° trans-2-Butene 16.2$ $ cis-2-Butene 12.6$

53

* bQ w

O

•H ©

0 v a. 1 oJ*

^.0

3.5

3.0-

2.5-

2.0-

RUN 21


0.097 M LITHIUM EIHOXIDE

[P^- P(olefin) ] = 5-657 - 2.833 t

0.5 1.0 t (hr.)

l.*f


% 1-Butene 6 0.7% % trans-2-Butene 21.2$ % cis-2-Butene 18.1$

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,b$2 M LITHIUM sec-BUTOXIDE

[P„- P( olefin)]2" = 6.502 - 8.372 t

0.15 0.3 0.5 t (hr.)


% 1-Butene *+8.3$ % trans-2-Butene 29-3$ % cis-2-Butene 22.h%

55

&0 W

a o

s •H <m 0 H 0 K 1 p}

3.0

2.5

2.0

RUN 30


0.061 M LITHIUM sec-BUTOXIDE

[P.O- P(olefin)]4 = .232 - 1.68J+ t

0.6 1.0 t (hr.)

1.5


% 1-Butene k-8.2% 1° trans-2-Butene 29• 2% % cis-2-Butene 22.5$

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.)


fa 1-Butene , k6.1% % trans-2-Butene 31.8% % cis-2-Butene 22.0%

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]

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


[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.

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 ]

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 • •

PS O o

no n o \0 m 0 1

en H vO •

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61

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62

RUN 38


0.076 M LITHIUM sec-BPTOXIDE

[P^- P(olefin)]2 = 3.571 - 1.89^ t

0.5 1.0 t (hr.)


% 1-Butene 1° trans-2-Butene 1° cis-2-Butene

63.7%

Vo.%

63

bO

a o

»S» I—I •H «H <D H 0 eC 1 o?

3.5-

3.0-

2.?.

2.0

RUN ^0



[P^- P(olefin) ] = - 1.757 t

0'.5 1.0 t (hr.)

T7¥


% 1-Butene 60.8$ % trans-2-Butene 20.5$ % cis-2-Butene 18.7$

6b

*bQ W

•H CH 0

H O

V-/ PH

p?

3-5

o 3.0

2.5'

2.0

RUN lj-1



[Pw- P(olefin)]4 = - 2.193 t

0.5 1.0 t (hr.)


% 1-Butene 60.0$ % trans-2-Butene 22.2$ % cis-2-Butene 17.8$

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

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

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

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.

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.

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