Hyperconjugation effects in substitutedcyclopropyl methyl ketones

Item Type text; Thesis-Reproduction (electronic)

Authors Lofquist, Robert Alden, 1929-

Publisher The University of Arizona.

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HYPERCONJUGATION EFFECTS IN SUBSTITUTED CYCLOPROFIL METHYL KETONES

byRobert A. Lofquist

A Thesis submitted to the faculty of the

Department of Chemistry in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE in the Graduate College, University of Arizona

1957

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The writer wishes t© express his appreciation to Dr® Milord G® Seeley for his guidance and invaluable assistance in the develop” ment of this work® :

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the Library to be made available to borrowers under rules of the Librarya Brief quotations from this thesis are allowable with«: out special permission provided that accurate acknowledgment of sotiree . is mdeti Bequests for permission for extended quotation from or repro duetion of this manuscript in -whole or in part may be granted by the head of the major department ©r the dean of the Graduate College when in their judgment the proposed use of the material is in the interests ©f scholarship© Im all other instances however , permission must be obtained from the author©

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The presence of alkyl substituents , and .paz-ticularly gem clialkyl■ substituents s on the cyclopropane ring, has been known for some time t©' ■ increase the stability, ©f the ringo ' The purpose ©£ this investigation has been to discover whether hyperconjugation of the alkyl groups with the eyelopropyl ring, was a contributing factor, in this added stabilitye' - In order to discover the extent ©f hypereoBjugatiohs use was made

■ of - the- ultraviolet absorption spectra® Bach work .has been done -in recent years in correlating,.molecular structure of organic molecules . with ultraviolet - absorption. spectrao The absorption of visible or ultraviolet light is usually associated.with an electronic displacement in the molecule» . The electrons displaeed are the w electrons which are

. excited from ,the: ground state into .a. state of higher energye The energy needed for this excitation is .less ,than .the energy needed to excite the : ((f ~. electrons s the eleetronswhieh form the primary - bond between atoms 0 It is about fifty times: the energy needed for vibrational transitions : and about -one thousand times the energy needed for rotational transit tionsA The. near ultraviolet- region which is usually defined as the

■ electromagnetic spectra from 200 to. &@@ lyi s is the. most easily meas=; uredd ’ " ' " .. - ■ '

-The spectra in this,region consists of a number of bands which correspond to different vibrational and rotational changes accompanying the electronic transitions®. If there were electronic transitions

without aeeon aoying vibrational and rotational energy changes only fine lines would, appear in the spectrum® However <, as the energy needed t©. eonvert the moleenle t© .an...:exeited-e|.eetronie state is- so much greater :. ■than the energy needed for a rotational or vibrational change,, these changes always occvr simultaneously®, As the energy levels for vihra= tioml and rotational levels are very close together broad bands appear-©, ■ To describe, the nature.-of the.7T electrons■ whose exeitatien pro= daces the ultraviolet spectra , the’ electrons and the normal single bond Bffiist be. described®

A molecular bond is formed when the probability envelopes of two electrons overlap sufficiently in spacers that iss when the wave functions■ 'Of two atoinio orbitals -overlap t©, sueh a degree that the probability of finding the electrons in that volume, is great enough to cause bond forma®- tion® Sehrldinger developed a three dimensional wave equation deSGribl% the motion associated with a moving electrons ,

ms*" ■45.where ^ is the amplitude' of the wave at any point: whose coordinates are xs :j.9 and %% m is the electron massg h■ is Planckrs constant| and w and v are its total and potential energy5 respectively.® The; degree of overlap of these-' W fmietiong' in a molecule is the. measure of the strength of the bond between two atoms in that molecule©

The solution of the SehrSdinger equation which is called an eigenfunction , has given quite an aeciarate description of the. hydrogen atom®' As' the atoms become more. eom )lexs certain approximations must be made-so that the equation is solvable0 The solutions- for the hydrogen-

_ •

like at©ms gives the following eigenf•unctions for the electron either in the K shell (principle qmntw nwiber equals 1) ©r the L. shell (pria®

.mmber' eqwls ■ 2) g • ’ ,. ;a Ira state '

1 0 0 Is

2 ©• '■ 2s C o . (Z oT/ "■ >

■ m f l ) cC/ * J /-£ ) ^ @I 4'#l5>r C ti./ ^ .

S is the eff eetive rraiaber of eharges on the meleuSi, a, is the smallest orbit of the normal hydrogen atom as given by the Bohr

' ,theeiyg r is the radial distancea

The val'tie 'of the' sqaare of the eig enf unction at- a point is, a, measure of the probability of finding the elee.tron at that point e .

The aorml earbon -atom has an eleeteoni® Gonfigaration'; of - ; _Is; 2s. 2px2py.j, that is$ two .paired 2s. and. two -unpaired 2p electrons im: its- outer shells As only the unpaired electrons contribute: to bond formation the valence might be expected to be two» However9 sinee, it- is known that in the. majority of carbon e©3?po‘mads it is quadrivalent: an' excited state ' of ls 2s2px2py2pB must be. postulated Heres however , since the px> py9 and pg orbitals are at right angles to each others it might be expected that three bonds of carbon would be at right angles and the fourth bond in no particular directien& Howeveri,. it is well-known#' and with, good ■

evidences that the bonds are arranged tetrahedralljo It is desirable t®correlate thdse-fsets with qmahtTam meehaBieal requirements e The express

'■ 9sion of the wave equation for earfoen in spherical coordinates ist

which en soluticn gives the following values, for and •np!s elee=

« /tronie. orbitals ®S /3 & cod &

. ~~(fS .M&s © <4^0

y%Pa ~f3 <s&& e

Prom these equations it appears that not only are the bonds not tetrahedral .but they are not equal' in bond strength* Generally5, the eigenfunction of the'-itprml siate of a moleeule is, a . linear combination of orbitals of states-of similar, energies0 The best linear combination is the one of least potential energyj, that iss greatest bond st

Q ' - . ^ Hfiy ? .

a limear combination of the fotar' orbital ^ .functions o The coefficients.ais eis and are determined through two conditionss firsts that the sum of the squares of. the coefficients in each bond eigenfunction equals qmeg and secondly that the sum of the products,, of the coefficients of any two eigenfunctions. is qer©>- for'::®£a» ies a ag b bg+c eg d dg® The soiutions of ^ , is ©r + 9^ c&6 O © Maximizingthis function gives a bond strength of 2<» at a (P equal to aerog ioe»s in the x direction® The solution of is

each, of these fmetions give a maxmmrbond strength of Z and are oriea=« . ted 1@9 2@9 from amd from eaeh others ■ These four bonds are referred t@ as sp3 hybrids1 and. constitute 'the tetrahedral’configuration of tetrad coralent earbono Actually$ It is probable that the bond angles will have these equal values only when all four bonds are'attached to identical- atoms- er groups» When the groups; are different the angles will ,differ to some extent from their ideal values and will result in a decrease in bond strengthb.'' » : -' ' '

When two sp hybrids ©Verlap a bond is formed with in the ground : state is called a Gq bond e, "ifhe bond is termed O' because of its deri= vation from the atomic s orbifals3'the subscript g indicates' that the 1 : wave has the same phase on both sides-of the center ©f symmetry between the nueleie The electrons participating in this bond are referred to as & ©lectronso These electrons are of opposite spizio ■ In the excited state one of these electrons passes t© a orbital (the SubscriptIndicates that the orbital has opposite phases across the axis of sym=> metry) without cMaage 'of spine - ,'

A similar treatment to that above ean be' applied to ethylenie bondingo The ■solution, to ■ the Sehrodinger equation gives three, bonds- 120® from''eaiefi others each icith a strength of 20©» The sp* hybrid describesthe position of "three of carbon9 s valence shell electrons& The solution'. ' : : ' : ' : . . - : ' ' > ' ' . . - to the Sehrodinger equation shows' that these electrons are oriented atright angles to the plane of the sp orbitals It is the overlapping of

6

two of these eleetrons wMeh form the 'bondg as a ground state & la the exeited state it ehaages te a orbital developing a new nodal plahe across the liak 0 The electrons which occupy this orbital are termed, electreas@ : ■:

Prior to this pronoioneement of electrons there was no adequate explanation for the doable bond not having twice the strength of the single bond, but as these "Tr orbitals are shown to overlap only slightly, it is easily understandable that this second bond cannot add greatly to the bonding force between two-'.carbon atoms joined by : a double bond®

is this overlap is not;as great .in-the case .of 7T electrons, it is easily seen that electronic transitions involving <r electrons; will require a greater energy of excitation than: the energy required for excitation of 7T electrons® Thus in saturated compounds this, energy is greater than liO hg-cal/mol, ; and the' absorption peak attending ' such a , v , transition will' fall: in the: far.' ultraviolet® ;Por' example, ethane shows a band maximum at 12Qmx while ethylene shows a btod system with a maxi* mum of 180 mjA ©

These maximums way be shifted by conjugation® Conjugation produces a bathoehromie shift in;..the absorption spectras This corresponds to , , . stabilising the molecule by lowering the activated state of ehremophoreso

Thus in butadiene there is conjugation between the double bonds which involve interaction of the molecular 77" 7V orbitals and contributing more ionic resonance forms to the total configuration® Just as ^ fume* fions'of bonds may be hybridised to give a mere Stable configuration, the .. more forms of approximately equal energy which-can be written for; the

7

struotnre of a molecule the greater is the stability of that molecule 0 In general these forms of approximately equal■energy:are limited to non-ionie and a few ionie structures0 The excited state of a molecule« howeTer# - iiyrolres a larger proportion of ionic forms o

This type of stabilization , know as conjugation, involves inters action ©f the molecular 7T orbitals.and occurs fn substances having electrons on at least four adjacent atoms® It cam be regarded as being built mp of non loealized ".7T orbitals superimposed on the orbital .skeleton -® Thus an olefin carbonyl system GsC=G-Oj, is also stabilised by conjugation® The, absorption maximum of ethylene is l85$iyx s while butadiene has a maximum at 217m)M and the olefin=earboiyl system has a . mmcimum at.22Qryz s illustrating the bathochromic shift due to conjugations This similarity in position of absorption peaks despite the replacement of the carbon by am oxygen is .characteristic! the only major change is that there is with the oxygen; compound- ■ a- newi? smaller absorption peak in the region of 2?5iyi e

In addition to the interaction between- a, double bond conjugated . with another double bonds there is also a stabilising effect due to inters ' action'of a double bond with a ■ single bond® This interaction of O'7T orbitals is termed hypereonjugation" ® It gives a stabilising effect similar t® that in .-"eonjtigated 'systems but not to such a degree This .rperconjugation is also termed lathan=®aker effect, by British chemists ®

Woodward^ has shown the hypereonjugative effects of alkyl substituents upon the ultraviolet absorption spectra of Ot imsaiupated ketones® Xt is interesting to note that only the % hydrogens seem to contribute to

' ‘ ' . < ' ' . ’ „ 1 • , ' '' . this i pereonjugatioB ffl .He showed that im a ketene ef the type' ' ' ~ - - -''» '-s C

whieh is smbstituted in the or |S position exhibits a maximmii in the region 225£5^u , disubstituted vioyl"ketones absorb in the region 23%$m^< and ^ spg “trisub stituted -rinyl ketones absorb in the region 25te5m^ 0 ‘Thus - the .smbstitution. of an gromp eanses; a bathochroinie shift of.abomt l . '

: Simi3a.r in many ways to the ethylene group, is the cyclopropane ring 6 Studies of its ultraviolet absorption give eonvinciaag evidence that the cyclopropane ring: has-electrons of . sufficient polarisability to-.conjugate -with an adjacent wisaturated gromp^o Ttos Klotz " reports that

' ' - /• «' ■ " i=eho2estadiene urhieh contains a c-c-cee linking shows an absorptionpeak of abomt 210m.jj.$ close to the absorption peak of butadiene» Alsosthe properties of a eyelopropyl'group attached to a carboxyl group arenot basically different from those of the corresponding unsaturatedcarbonyl eonpousds in several ’ reactions .s. In additions while the cycle® ’propane ring is reasonable; stable toward KMnO and 0.,. it is readilyruptured by catalytic hydrogenation or by the addition of halogens or

, ' Cyclopropane shows an ultraviolet absorption/m at TjQm.jj. $while propane has a ximciraw at and propene one. at ." This isindicative of its intermediate position between saturation and clef inie unsaturationb

Cyclopropane, differs ’ from an msatmrated -group in" several, ways0 lately5, Smith and Rogier^ synthesized 2»phenylbieyclopropyl and noted

that the data obtained from molecular refraction -ultraviolet and iafra« red absorption■speetra • and from its:reactions,.indicate that it does not shew any eonjugative effect above that" of eyelopropyitemenea Thus it appears that cyclopropane cannot enter into conjugation with anotiier cyclopropane ring©

. $he physical arrangement of the ' cyclopropane ring, Ms:, the C<=€•=€«, angles eqiaai t© 6® 3 with the GEg planes bisecting these angles.© The HCH angle might be expected to be abont ■ 120®e Pfom. different experimentss however the bond angle has been reported at from 98® to 136® e Pre= : bably the best e erimental evidence favors an angle of approximatelyii8®© ■ ‘ , . v ■ '.: ■.

The :6®0 ,C<=®=». angle precludes the ‘possibility-of an sp3 hybrid bond despite the tetracovaleney of the carbon atoms© Study of the dipole moment of cyClopropyl chloride offers rather strong evidence.that the carbon valencies toward the hydrogen atoms are ©lose to the sp2 hybrid : type^© .Walsh "® investigated the cyclopropyl ring on the assumption that ‘ three methylene groups in a ethylenie state are brought togethera and obtained fairly good qualitative agreement with experimental evidence e

Thus some electrons seem to ■ be' left over arid can become 77* @l§e== irons in molecular' orbitals and approach the olefinic 77’ eleetrens in nature© . ' This can give UBsaturation despite the absence of . double bonds, and" is called hyperconjugation as defined'" " Eullikem^^

Therefore, just'as the ’ultraviolet absorption peaks of. oc ,:(3 unsat<= -urated ketones are shifted by. the presence of alkyl groups attached in

the ot. or 3 positions s a similar shift of maxiimam absorptiea mght be expected, im alkyl substit-ated. eyeloprepyl methyl ketones j, although not to as great an extent® The present investigation was made to discover whether such a shift in fact takes placeo

BISGUSSIOH

The Gyelopropyl ring Ms approximately one-half of the tmsatm?™ atioa charaeteristies of etheylenie h©nds.»'s 'Thus hypereonjagation of ■ alkyl gromps with the' eyelopropyl: ring, might prodace a slif.ting ef ab#@rp« tioH peaks approximately half of what ' the similar alkyl group would effect when hypereonj-ugating with a double bond© Theoretical calculations indi®eate that this is the case©

■>' , ' . . . . ■ ■

Since eyclopropane absorbs at*approximately l6GmM2 hyperconjuga=tion of. methyl groups with the. simple ring would be difficult to observe ©For this reason.'a-'coinpouad was prepared which was conjugated enough tobring the. absorption peak into an easily measurable range© If hypereon®jugatibn exists then 2®methylcyelopr©jyl methyi ketone should shif t theabsorption peak to approximately 278myM© ; Biee- s however gives themaximum of 2-=>siethyleyleopr©pyl methyl: ketone as 265myu % in a .broaderbonds'. l:'li,2'=diiabtBylbyolopr@pyl methyl' ketone ■ should absorb; at approti® 'mately"'285nm ?jith a rather broad peak if hyperconjugation exists© .

¥o reference was found in the literatiare for the preparation of2s 2«=dimethylcyclbpropyl metlyl ketoneo Bice ® attempted the preparationof the confound by way. of mesityl ©xides which was dissolved in etherand an ether solution of diaaomethane was introduced©

12

N© reaction appeared.to oecur o - Although prodmeing gaseous diazomethane and introducing its freshly mades into the solution of the other.'reagen% has been found -to give a greater likelihood of a reaction taking plaee, this Method was not attempted because of the dangers inherent in the useof diasomethame@ ■- - ■: .'" ; 2i ' ■' ■ ■ ' ; ; 'Washburn attempted the production of the compound by eondensingisobmtylene bromide with ethyl acetoaeetate in the presence of sodiumethoxide©

»C-P>a + ^ ^ ^O sP £>;/ute Cx o

US!*

c/^

His product was a yellow=green liquid which polymerised "©n standing©This would hot seem to be the correct compound as its homologue eyclo- propyl methyl ketone is neither colored nor; polymerizes upon standing©He also attempted the synthesis by treating j>«bromo=$™methyl<=2-hexanome with an alcoholic solution of potassium hydroxide© Neither compound gave a Sgij.wdinitrophenylhydrasoseo. The; compound" was not investigated further.©.,

Upon searching the literature«, two methods were 'discovered.which might iedd to'the gem=>dimetliyl compound© The first involved starting with & -dimethylbermsteim aeid whose- preparation is given in'Vogel' 0

y , zC /Z/yoc-c(c^b C/^d^zy —^ / , v / f x<v

cT^cT 2

. !® , C\ 3 ri J? €&Ast&, €/% 0 ’■ 13

C^C-C^-COC^s ^ 2 ^ ^ JT^-COC-^ 4 T t c"oAr *"%C#2S» <% % C^c ♦

Cfr

c$ •> ?.O - "

This method folloiEs. the s@hem@ ©f:Blames'as reported la Beil-”:- stein to ge% the 2; 2=d±methyleyelopropyl carbosgrlic acid and the method of Bruylantg^ to get the ketone 0

The seeond method found was similar to the preparation of eyelo-= propyl methyl ketone as deserihed in Organic Syntheses o The only change involves starting with isobutylene oxide instead of ethylene oxide and the reaction proceeds aceordiaag to the following schemesA&og-cA'f -t //sC'Ccm£c o c 2hs ^ 3c-c-c-~ex- c ' - . . _ L _/u

&>

/V

This second method was chosen beeamse fewer steps and more available starting material were requireda

Both of these methods should be more successful than the methodg n ■ ■ ■of Washburn* s sin.ee in both of these reaetions the chloride formed is

the more stable primary chloride and thus is less likely to isomeriae and polymerize© ’ : '' '

Hi

Two methods of synthesizing isobutylene oxide were attempted® Both involved first the dehydration of t bmtyl alcohol' with, sulfuri© aeM27. ' / , : / V: : v ; ; y;"

In the first method the gas was. bubbled through monoperphthalie acid as the isobutylene was formed®

/ ^ „ ? <r"3 o „ 'L.nr -oeYields of the monoperphthalie acid were lower than expected and there was no yield of isobutylene oxide® : : ; . /': ' . .' /

In the: seeond method; the isobutylehe was bubbled through bromine : water to obtain the bromohydrim ® There was no significant increase in yield by ©©©ling the bromine water so as to cut down on loss of bromine vapor® ,:JL good yield of bromohydrin resulted®

• An attest to produce the epoxide by heating the bromohyirin ia the presence of aqueous sodium hydroxide was unsuccessful as the material dissolved in the water and could not be separated by distillation®

The second method tried was continuous distillation of the epoxide as it was formed in the- sodium -hydroxide solution® In this1 manner. a, good , yield of isobutylene oxide'was' produced®. - '

To make the h=»lactone of 2=-aeeto= 3' $, 3 dimethyl h hydro butanoie acidg acetoacetie ester and isobutylene oxide were dissolved, in ethanol and allowed to stand for two days. ® The yield was not as great as ;

This lactone is believed to foe 3s3=dimethyl rather than ksk™ dimethyl becamse of the. apparent stability of the chloride formed and because in the ring opening of the epoxide a tertiary earbonium ion . would be formed which - is, more stable than the primry earbon ien0 If the tertiary earbonirjh ion is formed then the product will be the '.3S3= dimethyl eomp©md| howevers it is reported that in the ease of unspi=- metrieal ©xidess ring openings in basie solution" are almost always such that the least substituted., carbon atom is attacked by the nueleopMlie reagent ®s in this ease the sodium salt of aeetoaeetie ester0 As either eompoundg if eyeliaed , would result in the same ketone r this chloreketone was not structurally investigated®

The eyclls&tiom followed the scheme In Organic Syntheses^ @ in ■ which the ehleroketone is added droptfise to concentrated sodium hydrox- - ide| the solution rsfluxed for two hours and then steam distilled until smoke appeared in the flask® .The remaining material solidified and there was: evidence of appreciable gum formation® . :

. The distillate separated into two layers and the upper layer, was . distilled at, atmospheric pressure® Distillation started at 156° with decomposition® The reaction was repeated and the product was distilled at 36mm® pressure without decomposition® ;. .

This eojfigjound is believed t© be 2s 2=dimethyleyelopropyl methyl ketone on the basis of infrared studies- made on it and on mesityl oxides and. on the basis of its ultraviolet absorption spectra® -

Comparison of the ultraviolet absorption maximum of the cycle® propyl methyl ketone with the 2s2“dimethylcyclopropyl methyl ketone shows

.. ■ ■ •, . v ' . , : 16

that the absorption maximum is shifted oxxl' te the red which is less than/ the, , -of.: the ' spectrophotometer@ My hyperconjugation effectshould be approximately: fire- times this' amount*: Since the position of the maximum is a measure of the difference between the ground state and the first excited state in the molecules it appears that the presence of the gem-dimethyl configuration does not contribute by hypereonjugation to the excited stateo- ' ': 1 .7 - ■ ' ; 1

Perhaps as Smith and Bogier’s work also indicates,, the eonjnga=. • tion of the cyclopropane ring cannot trammit labile electrons from one end of the molecule to another§ but can only supply them to an umsatur ated group.®: - ■■ ,/

EKPERBEMTAL

Preparatlem.'of Mo.mo#@rphthalie aeM: : : ; - -Monoperphthalle acid was prepared aeeordiEg t© the directions

given in ©rganie Syntheses . , / ' .

Preparatien. ©f,,Is©bm%lene.. ■ ' ' "' - , /'■ , ' . ■ '_■•■■■' 27 ■ Isdbutylene was prepared according to K'istiakowsky et al o The

isobutylene was washed by bubbling through sodium hydroxide solution;®

Preparation of 5°°bromo<”2°-methyl°2 propanol , ; . . -■ - 28 ■ •Bead, and Reid's directions for making the bromohydrin of

"isoarrylene were modified using ten . times the molar quantityc The isobutylene formed from Ui8 g0(2 moles) of t=butyl alcohol and 10 ces® of concentrated sulfuric acid after passing through dilute sodium hydroxide solution was bubbled into bromine water« The bromine water was prepared by adding 229 go of bromine to a solution of 2QQ gQ of potassium bromide In three liters of water 6 An oil layer was formed at the bottom of the flask® It was separated and the water layer was .extracted $ times with 300 ml® of ether® The ether extract was added to the Oil layer® This solution was dried with anhydrous sodium sulfate The ether was removed by distillation® The remaining liquid was dis= tilled at 35mio pressure giving a yield of 392 gos kS per cent theoret®7 ical yield® The boiling point range was 55=6° at 35mmQ pressure® The

density was 2^8 at 2$® eo^ared Hith water at ...■ ' Reported BSP6 50° at 3&mo^^ ;' , ■'/

Preparation of Isobmiyiene oxide: ' 1 1In a 2=liter tbree neeked flask was placed a solution of I4O ge

of potassium hydroxide im $00 iti,o "of water» The flask was equipped with a $00 mlo dropping funnel and a condenser set for distillation The solution was heated ©n a water hath and the hromohydrin was added slowly» The epoxide; began distilling, immediately and the vapor temperature wasnewer allowed to go above- 6®®*- The. boiling point of the epoxide after .drying over anhydrous sodium sulfate was k9Q at 700 mo The yield was , 12k g@ (66 yield)@ .

Preparation of the k«lactone of 2°aceto°3 93°dimethyl ktehydroxy«°butanoic..acid : ' ' .

. " " ' ■ - ■ : " ' " . . ! ' : O Q -■ . '. 1 ' : :Followi% the general scheme of Knunyants 7 et ale, 72 g® of isobutylene oxide dissolved in 60 mle of absolute ethanol was cooled, t©5® and added to. one mole.of the sodium salt of aeeteaeetic esters dis= solved in 1$©© bee* of absolute ethanol at 5°® The mixture was put in an ice bathg allowed to warm up slowly to room temperature and kept at room temperature for 2% hours® . ,

After the ethanol was removed under reduced pressure the residue was decomposed with 6$ grams of glacial -acetic acid® The lactone ■ was then extracted with ether until the ether layer-was colorless® The ether Xayer was dried with anhydrous sodium sulfate and distilled® The product boiling at 153® at 38 mm® was collected® The yield was go

P epagat-ioB. of S hoTO bMllmethyl g peataaeneA modlfleatlon of the procedure described■' in Organic Syntheses ..

was ttside A’ mixture of ml0 of concentrated hydrochloric aeids 5© mle- of water and k& go of '2«=aeet©y3s3adiH@thyl=i;»batyrolaetone was placed in a 300 ml© flask© The condenser was cooled with ice water and the receiver ■ was immersed in an. ice batho Carbon dioxide was evolved immed“ iately® Heating was begun, and sighty foaming beeurred6' In about' ten minutes the color changed from near=>eolorlesss to yellow to ©range/ to: black© distillation started immediately©.

The distillation eontMmed until there was no more than. 20 ml© of water Ibft ih the distilling flask0 Then an additional itS mle of water 'Waa added and 30 mle more of distillate was collected0

After adding 5 ml® of ether, to the distillatethe organic layer was separated and dried over calcium chloride for one hour© The ether solution, was then decanted and dried over fresh calcium chloride for another' hour© The ether was removed by distilXatibns leaving the crude ehloroketoite © The yield of 5"ehlor0'»ij.<,lt=diniethyl<=>2 pent.anone. - was'! 19, grams c w yield)©;' • :

Preparation of 2$ 2~dMethyleycIopropyl methyl ketone ...A 200 ml© Sleeked flask, was' fitted with a Hershberg stirrer a

dropping funnel and a - reflux eondehSer© A solution of 10 grains sodium 1 hydroxide in 10 g© of water was placed in the flask© 19 g© of the chlbrokbtone were added over a peziod' of ten miMteSo

-20

■ The reaetim mlxtm*e,wss Meated. so that it 'boiled slightly»1fter the' itrijeture was -boiled fer one houry 20 mle of water was added ■■ over a ten minmie periods The mixture was then heated mnder reflvoc for another hour<> ' •■ . ‘ Mter an, hour the condenser was.arranged for distillation and a; .,

water ketbne mixture was distilled until smoke appeared in the flask® During; the entire reaction and distillation the stirrer was kept in oper=■ atim® ; . - ' ■ • , \ • . '

: . The aqueous layer ofthe distillate was saturated with sodium .carbonate and the ketone layer separated® The ketone layer was dried over calcium chloride for one heurs then decanted and dried over addi®• tienal calcium chloride® - The:ketone - was distilled at 36 mm.® over a' tez#er ature range of

Ultraviolet absQrption spectra. ..■ v -' The instrument:; used t© obtain" ihe ultraviolet spectrum was a, .

leekmang Model BW Ultraviolet spectoj>hot©meter® The solution of 2S2<=> dimfhyleyclopropy1 methyl kefdne was'loJSxlO molar with. 95% ethanol used as the solvent» Figure I gives the ultraviolet .absorption of eyelopropyl methyl ketones 2s2"dimethylcyelopropyl methyl ketones and mesityl oxide® '

The instrument used to obtain the infrared spectra was the Beckman Model IE“23 with. recorder® A sodium chloride, prism was used®The cell material was rock salt® . ' ; ’ , ■

; The speetra: was •fcakem,' ©s.: the pwe ees emdo The speetra ©f . mesityl ©xide and 2g 2=dlm©thyl©ycl©pro rl methyl ketone are given in Figure 20 ■ The peak of the eyelopropyl ketone is within the range

SUEfflRY AE) GONCLUSI01S

Three new eonpouBis were prepared ,(a) The lactone of 2”3.eet©=3s3adimethyl”l£»hydro2cybutaHQic heiis ■

a ■ colorless liquid with an odor like aeetoacetie estere The boiling point wasl53® at 38 imao ' ;

'(is). 5 hlor©-Ma iimethyi^pentanone* v \ . . •(ej: 2S2=dimethyleycl©propyl methyl ketones' a colorless oil with• &: sharp odor similar .te aeetone The boiling point range was ,

, at 36 mmo pressure© :The. infrared spectra Of mesityl.. oxide ' was compared with 2$ 2=-diiaethyl=» eyclopropyl methyl ketone* It was conelixded that the spectra showed the absence of doable bond ujisaturation in the cyelopropyl ketone, and the presence of the cyclopropane, ring®The ultraviolet absorption/spectram of 2s2~tiimethylcyclopropyl ’ methyl ketone was compared to the Bltrsriolit. absorption spectrum of cyelopropyl methyl ketone® The primary absorption peak of 2a2« dimethyleyelopropyl methyl ketone showed no shif ting toward the red compared to the position of the primary absorption peak of eyelo*= propyl methyl ketone® From this it was concluded that hyperconjuga” tion between the methyl groups and the cyelopropyl ring does not V

OGS

CTCLOFROm METHYL KETONE3.5 B 2, MIMETHYLCYCLOFROPYL

METHYL KETONEMESITYL OXIDE

3.0

2.5

0.5

2 3 0 2 9 02 7 02 5 0210 310 3 3 0/ryU

FIG I

— I--------------- 1---------------- 1-----9.23 989 10.50 yi

FIG 2A 2,2-DIMETHYLCYCLOPROPn, METHYL KETONE B MESim OXIDE

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