A graduate student was following a procedure to make 3-propylcyclohexa-1,4-diene. During the workup procedure, hisresearch adviser called him into her office. By the time the student returned to his bench, the product had warmed to ahigher 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 cm-1as opposed to the literature value of 1650 cm-1for the desired product.The mass spectrum showed the correct molecular weight, but the base peak was at M929 rather than at M943 as expected.Because of the anomalous IR spectrum, he took a UV spectrum that showed lmax at 261 nm.(a) Should he have his IR recalibrated or should he repeat the experiment, watching the temperature more carefully?What does the 1630 cm-1absorption 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 M943, and show how your proposed structure would give anintense peak at M929.
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 cm-1
as opposed to the literature value of 1650 cm-1
for the desired product.
The mass spectrum showed the correct molecular weight, but the base peak was at M929 rather than at M943 as expected.
Because of the anomalous IR spectrum, he took a UV spectrum that showed lmax at 261 nm.
(a) Should he have his IR recalibrated or should he repeat the experiment, watching the temperature more carefully?
What does the 1630 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 M943, and show how your proposed structure would give an
intense peak at M929.
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A graduate student was following a procedure to make 3-propylcyclohexa-1,4-diene. He overheated the product. He isolated the product, which gave the appropriate =C−H stretch in the IR, but the C=C stretch appeared around 1630 cm−1as opposed to the literature value of 1650 cm−1for the desired product. The mass spectrum showed the correct molecular weight, but the base peak was at M–29 rather than at M–43 as expected. Because of the anomalous IR spectrum, he took a UV spectrum that showed λmaxat 261 nm.
- Draw the structure of the desired product, and propose a structure for the actual product.
- Show why he expected the MS base peak to be at M–43, and show how your proposed structure would give an intense peak at M–29.
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