Question

Describe the characteristic infrared absorption frequencies that would allow you to distinguish between the following pairs of compounds (a) 2,3-dimethylbut-2-ene and 2,3-dimethylbut-1-ene (b) cyclohexa-1,3-diene and cyclohexa-1,4-diene (с) CН:(СH>);—С—н аnd CH:(CH)2 —с- (d) CH,СH,CH,—С-NH, and CH,CH,—С-CH-CH, CH pentanal pentan-2-one butanamide pentan-3-one ОН (е) СH:(СH>)5 — С—с-н and CH3(CH2)6 — С%3DN () CH,CH,CH, —С— ОН CH —CH—CH,—С—Н and octanenitrile butanoic acid 3-hydroxybutanal oct-1-yne

Answer 1

dlescribe to charact We ve According in frared absor ption freg uentuies V) to the 9uestion, -iristic to distinguich ,3- iethylbut-A the toll - Lbut-aene and 8,3-dimethybur ene C C -Ch 3 CH 3 2 that know As We uen where k: bond constant, reduced MMass tronge will te w be its e. the more Streng th the more bond the Stret ni bra tion to gbsorb I-R. dipole the mo ment radiation, chang when vibration sccurs. Hence molecule. must it i's I-R- in activl и show SOm e However ^ l600 cm- eyclohexat, u-diene i's and hexadi ent metrital Jhd hene its 3 ifoleniohaentu) 1 TR. ingi- This ill show som charactenis tic I R stretehi'ng V tess than 600n

bent-- one c Pentanal and в сиз- в си-иy chyg СH3 Cиз сн сн Ne S cm -C-H > st hat, electro n dona tingros alee a love As know we C 2 deereases the ) Hence shown CH D dy Butana mide and þentan-3-one сHg сen,-сn -20in, Сиз -сн, ё-cugclyg Cag St. due to reson ance No resonance, +I ettet сHз си, -си, CENH both