A graduate student was following a procedure to make

QUESTION:

A graduate student was following a procedure to make 3-propylcyclohexa-1,4-diene. During the workup procedure, his research adviser called him into her office. By the time the student returned to his bench, the product had warmed to a higher temperature than recommended. He isolated the product, which gave the appropriate \(=C-H \) stretch in the IR, but the \(C=C\) stretch appeared around \(1630 \mathrm{~cm}^{-1}\) as opposed to the literature value of

\(1650 \mathrm{~cm}^{-1}\) for the desired product. The mass spectrum showed the correct molecular weight, but the base peak was at rather than at as expected. Because of the anomalous IR spectrum, he took a UV spectrum that showed max at \(261 \mathrm{~nm}\).

(a) Should he have his IR recalibrated or should he repeat the experiment, watching the temperature more carefully? What does the \(1630 \mathrm{~cm}^{-1}\) absorption suggest?

(b) Draw the structure of the desired product, and propose a structure for the actual product.

(c) Show why he expected the MS base peak to be at , and show how your proposed structure would give an intense peak at . \(M-2\)

Equation Transcription:

Text Transcription:

=C-H

C=C

1630cm-1

1650 cm-1

261 nm

1630cm-1

M-2