Chemistry 332 - Spring 1996
Elements of Organic Chemistry II

Quiz, Chapter 13 - Structure Determination

1. (4 points) Complete the following short-answer questions:

a) The 13C NMR spectrum of ethylbenzene will have __6__ different absorptions.

(Two different carbons in the ethyl group and four different carbons in the benzene ring.)

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b) A C8 compound with an ultraviolet absorption peak at 230 nm is more likely to be :
ethylbenzene
*** 2,4-octadiene ***
2,4,6-octatriene

(Dienes absorb around 220 nm, benzenes and trienes around 260 nm.)

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c) The compounds 1-octyne and cyclooctane can be readily distinguished by their IR spectra because only 1-octyne will show characteristic absorptions in the ranges of __3300__ cm-1 and __2200__ cm-1.

(Characteristic C-H stretch for sp hybridization and C-C triple bond stretch.)

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d) The presence of a carbonyl ( C=O ) functional group is easily detected in the infrared by an absorption in the range __1700__ cm-1 and in the 13C NMR by an absorption in the range __200__ ppm.

(Characteristic peaks for carbonyl groups.)

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2. (6 points) NMR spectra of three different isomers of C4H8O2 are shown on the back. All of them are found to have a carbonyl group. Identify the structures of compounds a, b, and c.

a)

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b)

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c)

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