and Eicke 5. 01ren2 Frerno State College Fresno, Colifornio 93726 ond Leland A. Smeltz Bloornrbvrq Stote Colleqe Bloornsburg, ~e~nrylvonio 17815
1 I1
Structure Elucidation A n organic chemistry experiment
T h e rwrnt intrrrst ( 1 ) in drrrloping rxprrimrnt* rvl~irl~ olTrr n mrrrlntion lwt\rt.en m o t l r r ~ ~ orpnnic tlicory nncl prnrtirr prontptr [IS to rcport nrl orpnnic strr~rturc~ rh~ricl:ltin~~ rxprrimrnt wlrich is I~nsnl ~
~~~
n o r t r r r i n l s i ~ ~ r l ~the ~ d prq~:irntion w of two isnmrrs : ~ n dn4~111nr11t of s t r w t u r r i ~ f t r ir~ ~ t r r p r r l n l i o n nf t h r rrslvrtivr nmr, nnrl to n lrssrr r x l n ~ l uv , nnd ir, 1 t r n . l'hr t\vo isomrrs. ('2,H,0,. I nnd IT, I.'ig~~rrs : ~ n d2 rcsprrtivrly, a r r prrp:~rcul from mrthonr (5..% rli~l~rlhyl-l.:&ryrlol~rx:~r~~liot~(~) Irg wing the. sli~nrl:~rd iclrntilirntion prorculurr fnr rh:~r:~clrriringnlrlr11ydr.r ( 2 ,.i). i~~vnlving r n n v r r ~ i oto~h~i s n ~ r t l ~ n(Irriv:rtivrs nr Isomrr I i* t11r 11ormn1,cyrlirrd I ~ i ~ n r r t l ~ (Irrivnonr tivr of ~ + m r t l ~ o x y h r r ~ m i ~ l r l ~TIII. y ~ linitially r. fnrtnnl ng ~ ~ n r y r l i r ndrriv;~tivr, l I l l , i* prepnrnl I I I~ ~ r n t i ~a ~ n r l ~ ~ r n rnlrol~olic ~" n d u t i o ~of~mrthonr and t h r eldrhy(le in t h r prcsrnrr of :I drop of pipericli~w. Rcrrystn1lia:rtion from :in nqrlrnw, i~ridic,rtl~nnolsolution promotm drl~yclrnlionof t h r intrrn~rdintrto yirlrl isomrr I ~vhirh is thrn s r ~ l ~ j r c lto r ~sprrtrowopic l rsnminntin~~.
I.
ngun 1.
NMR s p . r t n n of 1M.r
Figure 2.
NMR s p M n n n of h e r 11.
nclduct. IV, r~nknownfor sevrrnl ymrs (.?4i) is the s r ~ h atitutrd hrnropyrnn inclicnt~rl(7. 8) nnd nrisrs by nn altrrnntc ryrlia:~tionpnifl. 0-methyintion of IV with climrtl~yls~rlf::tri l l h s i c tlimethoxyrthnne, ronditiona wl~irlifxvnr 0-nlkylntiou of 8-dikrtonrs (8), yields the T h r p r r c ~ ~ r w risomrr of I1 is p r r p n r ~ in l nn nnnlogorts swond iwmer, 11. rnnnner. Ily rrfl~~xing :in nqllrnus, nlcoholic s o l u t i o ~of~ A compnriro~~ of the ph,vsi?nl properties of the two r of piprrim r t l ~ o n rrind snliryl:~ldrhsdrin t l ~ prrwner dinr. T h e strurl urr of t 11r initin1 snlirylnl~lrl~y~lr isomers prrpnrnl rwrnls to t h r studrnt nt onre tirnt h r is d n ~ l i n gwith two clitTrrrnt r o m p o ~ ~ ~ ~In d sfnct. . the prrvio~wsrt of r r n c t i o ~ ~issprrhnps tlw simplr.*t method of shoxving that in t hc rnseof the salicylnl~lrl~yclce~lrrivntivr t l ~ rr~sunlcyrlisntion pnth yic*lclinp :I r ~ ~ l ~ u t i t u t r d octnhyclrox:~~~thet~(is not nprrntivr, since if it ~ v r r r .
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laurn01 of Chemical Edudion
0-mrthylntion \roulcl yirld an 0-mrthyl rthrr iclrntienl to I nnd not the isomrric hrnzopyrnn. 11.' i n 1:intrrs 1 n t d 2, clrnmo~~T h r nmr sl~rclrn.shoxr~~ strntr thnt nurlrnr mngnetic rnollnnre sprrtroscopy is n po\rrrful nnnlyticnl tool in structnrnl cluciclntion. Although there nre twenty-right hyclrogens per inomer, moleculnr symmetry and the lack of spin-spin splitting (with the sole excrption of the nromntic multipletr) pmvklr for simplr sprctrn. Thus, with the rxcrption of the aromntic nhsorptions in rnch isomer the rrrnnininpsinglrts rrvrnl n structr~rnlsit~~ntion rrquiring t h r nhsencr of ndjncent cnrhons which h t h henr hydrogrns. In enrh spertrum thr signnls dnr to the trrtinry hrnrylic hydrngrn, thr nromntic hydrogn~s,nnd the 0-mrthyl hydrogms nrr mnsistent with expcctd chrmienl shifts :u~cl rrlntivr intmsitiw. T h r most noticrnhlr nncl rrvrnling differences nrr thnt in thr cyclirnl ~mrthonyl)rnraldrhydrhismethonr clerivnt i w , due to t h r symmetry of the f w d thrrr ring systrm, thrrcnrr two differrnt (:-methyl hydroprn singlrts, n singlet for t h r four nluivnlmt rrkrto hydrogrns nnd n singlet for thr four cquivnlrnt nllylic hydrogrns. The mrthylnterl snlicylnldrhydc derivntivr exhihits n ~ p r c trum ehnrnctrristic of lrx* symmrtry. T h r ~ ~ o n q u i v n h e r of the four pnirs of met hylrnr hydroprns is rrndily nppnrrnt. Thrrr nrr t hrrr C-mrt hyl hydrogen singlrt s in thr rntio?: 1: 1, which indientr thnt thr 1tvn C-mrthyl groups on thr unfusnl ring have n slightly diffrrrnt chrmicnl shift thnn rither the C-methyl group nlmvr or t h r C-mrthyl group l~rlowthe hrnsopyrsn fusnl thrre ring systrm. Somr studenta nppmr snsprct when it is s ~ g g w t r ~ l thnt the conversion of 111 to I is nccomplishnl hy mrrr rrcrystnllizntion from aridic, nqumus ethnml, rsl~rci:~lly when thry ohserrr thnt thr melting pnints of rrnrtnnt nnd product nrr within 1-2' of rnch othrr. In nddition to prrforming n mixturr m r l l i ~ ~pnint g clrtrrmi~~nlion, v r hnw found it usrful to show that n rrnction hns Inkrn plncr hy n mmpnrison nf ultrnviolrt nnd infrnrnl sprrtrnl chnngw. T h r ultrnviolrt sprrtrum of t h r unnt 26i mp which shifts ryclisrrl elrrivntivr. 111, hns A,., to .A., nt 2?!) mp OII the ncklition of n drop of 0.1 N sodium hydroxitlr, indicnling the prrsrncr of nn rnolia I functiou i n h i l r r i r ~ ~ ~ i vTrh. r cyclirnl deriwtire, I, hns nl~wrptionsnl 221, 236, nncl 296 mp4 i n rithernrutrnl orhnsic rthnnol. I n n similnrmnnt~rr,t h r
disnppmmncr of the OH function cnn hr shown hy n compnriwn of rrnctnnt and product infrnrnl sprrtrn (11).
Experimental
Birrnethorn Derivatives of o-Mefhoxybanmldehyds (2, 3)
Bismethone Derivative of Solicyloldehyde ond its 0-Methyl Derivative
Aclrnowledgmenl
Likmtum Cited
~olurne47, Number 3, March 1970
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