有机化合物波谱解析课件 综合练习题及答案_第3套.pdfVIP

SPECTRUM ELUCIDATION HEBEI UNIVERSITY OF SCIENCE AND TECHNOLOGY Comprehensive Exercises 3 Try to do the exercises by yourself, then go to the answers and think why. Problem 1. Compares the λ and ε of the following compounds: max max Ethylene; 1,3,5-hexatriene; 1,3-butadiene. Answer 1,3,5-hexatriene 1,3-butadiene Ethylene Problem 2. Ionone has two isomers, the absorption maximum of αisomer is at 228nm ( ε=14000), and the absorption maximum of βisomer is at 296nm ( ε =11000). Match the UV spectrum with appropriate compounds αand β. H C CH O 3 3 1 CH C C CH3 H CH3 2 H C CH O 3 3 CH C C CH3 H CH3 Answer 1. β 2. α Problem 3. The n→σ* transition can appear in (CH ) N, the absorption 3 3 maximum of it is at 227nm( ε=900). In the acid solution, how does the absorption maximum change? And give the reasons. Answer The absorption made by the n→σ* transition disappear. Problem 4. Looking the IR spectrum for one compound, it has 1700cm-1 (s) 3020cm-1(s), indicate which of the four given compounds is responsible for it? (1) O (2) CHO (3) C CH (4) OCH CH2 Answer (2) Because the absorption in the 1700cm-1 region indicates that the -1 compound has ν , the absorption at 3200cm indicates that the compound contains c=o a benzene ring.