Howard Alper' and Anne E. Alper Stote University of N e w York ot Binghomton 13901 A ~ e Taurinr d McGill Univerritv Montreol, ~ o n o d a
I II
Ring-Chain Tauhmerism A n experiment in organic chemistry
Tnutomerism is nn i m p r t n n t concept. (lisrr~ssnlin all i n t m d ~ ~ r t o orgnnie ry trxts.? The most. comnion typr of t:~utomrrism involvrs n shift of n proton fmm one atom to nnothrr (penrrnlly rrfrrrrd to :IS :I prototmpir rhange), r.g., keto-mol nod rinp-chnin tnutomrrism.a rnfortnnntrly, rsprrimrnts drsignrd to illustr:~trthis ronrrpt nrr u s ~ ~ n l not l y inrludrcl in the lint nrp:lnir 1:rhoratory course. T h r following is 8 d c srription of n sin~plrrsprrimrnt in ring-rhnin tnntomrrism.
da (I svns not sufirirntly soluble ill rhlomform-rl for nmr sturliw) n t d rlrnrly indirntrcl thnt t h r t:ultonirm In nnrl Ih w r r present in a I : ? rntio. T h r fnllnwing fenturw of t h r nmr sprctnlm nrr notrxwrthy: thc t!w pmtons in the mrthylrnr group of l h nrr rcluiralrnt rtncl givr n singlr nhsnrptirm $11 6 43.; whilr tlw n ~ r t h y l r n r pmtons of In :Ire not~rc~r~irnlrnt nnrl nppe:w ns :I qunrtrt rr~~trrw ntl 6 :{.!M;s i ~ ~ g l ew t s r r o h s r n n l nt 6 ].!I4 for the methyl protnns of I:I :incl nt 6 '?:.'L for t h r mrthyl protons of Ih. This rxprrimrnt cnn he r o m p l r t ~ lin txw Inhorntory prriods. S~~pprstions for f ~ ~ r t hwork r r incluclr: ( 0 ) n study of t h r snlrrnt cfTrct on the position of the t:111tonwrie nluilihriwn (rnrthylrnr rhloridr nncl l,2-1lirhlomrthnnr nrr some of the othrr solrnrls whirh hnvr
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ran hr prrparrcl hy rondrnsntio~~ of t h r :~ppmpri:itr a-chlomlirtonr with 2-hr~izin~irl:~rolirlrtl~ior~c~: ( r ) drhyclrntion of In with i r ; I~yclrorhlorir:wid to pirr 3mrthylthinzolo[.?.l'n]br~~xin~i~l:~zr~lc~' ( s t ~ ~ d r n t wrrr s :1-IIyrlmsy-.?-mrtl1yl-2,~-dihy~lmthi:1zolo~3,2n]hmrnhlr to cnrrv out t h r ~ l r h r c l r n t i ~ rrnrtion ~ n ill 88-!3tiC: imirlnznlr (I:,) rnn rsist in rquilihriuni with its oprnrhnin nminokrtorw t:wtomrr Ih.' This syslrm tvns rho.ur~~ for t h r ~ q r r i m r n tfor t h r follow in^ rrnsons: The Exporimon1 tlw r : ~ r h i ~ ~ o l : ~ m r:m i n rh r e : d y prrp:~rwI (it is nlsn n p n r l rs:~nqrlr of :I ron(lrnsntion m ~ r t i o n ) ;t h r ta~ltotnrrir nluilihrium rtin h r rr:alily s t r d i t ~ lby infrwrrl (ir) :lnd p:irtiruInrly nurlrnr m:~nnrticrrsnnnnrc (nmr) s t l t l n i u ; nnd this c q ~ r r i m r n tm:Iy he usnl :IS :I st:irtinp pnint for other simplr i~~rrstigntions. T h r hrtrrnryrlr I:\ is oht:tinnl in nr;~rlyquantitntivr yirkl ( r r r u hy t h r Irss skillrcl stwlrnts) by t h r condrns:rt inn of t h r rr.dily nr:iil:~hlrmntrri:~ls,2-hrnzimicl:nolin~~thionr nnrl rhlom:~rrtn~w, in 2-hutnnonr. T h e i ~ ~ f r : ~ sr ln~l r r t r r ~ rrf m t h r proclrwt ns n potnssiwn h w niillr disr shows thrtt its s t r ~ ~ r t u in r c the wlid st:~tris th:~t of the ryrlir c:whit~ol:~n~inr In ( S n t v t : ~ ~ ~ t n m r r i c nluilibri:~of t l l r type I:I F! Ih orcur only in snlution or in I I i ~ ~r i l: I S s t n t ) . Rmnd nhsnrption he~ \ W C . I I :VW ilncl 2liW rm-' \vas r ~ s s i p ~ ~ l or dt h r 0 - H strrtrh (PI l h I~y~ln~gn~-hnnclNI ~ hyrlrosyl gmup. In ndditinn, :I stmnp h:tnd :tt l0X.i rm-' for l h r ('-0 strrtrli of :I tvrti:iry nln~hol: ~ n d:I hrond hnncl of m m l i ~ ~ inm trnsity : ~ l1:{43 rm-' for t h r in-plnnr 0-11 &-forrn:~tion ' To whom inquiriw ~houlrlhr n d d l ~ w l . :Irr : ~ l wc~hwrrrcl. Scdutior~infr:~rrcl spcrtr:~i~dir;\tr ' hw ~snrnplr,r w : 1") ( k s v , I I. J . , . s s n I1 ~M.UOSI>, (;. S., tlw prrsrllrr of :I n i i s t ~ ~ rofv t h r t:ultornrrs In n ~ lh. d "Organic ('hemidry," f h l I X I , .!lciirmv-llill I h ! k ('ompnny, , I hr infr:~rwlspn-trim i l l rhlornform s n l ~ ~ t i nrshihits n n 11, T,,.$st) Iknn, Sew Twk. 1964. p. 2'll-:
