2 questions: Experimental: Reference: This experiment In the current experiment

Question

2 questions: Experimental: Reference: This experiment In the current experiment you will dehydrate cis/trans-4-methylcyclohexanol to form 4-methyl- 1-cyclohexene using concentrated phosphoric acid. Sulphuric acid is a much stronger acid that phosphoric acid, but phosphoric acid will still promote the dehydration reaction via carbocation formation, and will avoid the possible side reactions that can occur with sulphuric acid. The product alkene will be removed by simple distillation and analyzed by IR and NMR spectroscopy.

Explanation / Answer

In the conversion of 4-Methyl-cyclohexanol to 4-methyl-cyclohexene,the main functional group that is coming in is a double bond.

(3) The double bond -C=C- has a stretching frequency at 1620-1680 cm-1. When weexamine the spectra obtained after the reaction, we see that there is a peak at 1652 cm-1 which is also a signature peak in the reference spectrum. (but this should not be present in the alcohol).

Other peaks due double bonded carbon are =C-H stretching at 3010-3100 cm-1 which is again present as a sharp peak after the broad peaks near 2800-2900 cm-1 (due to C-H stretch). This is also a peak not expected in the alcohol.

There are also sharp peaks in the range 675-1000 cm-1 due to =C-H bending

So we can say that the raection forms 4-Methylcyclohexanene due to the reference peaks of unsaturated double bonds as mentioned and which matches with the refernce spectrum.

The next question asks if there is unreacted alcohol present. The answer is yes, beacuse we can see a broad peak of O-H stretching which is strong peak above 3200 cm-1. The peak is absent in the refernce spectrum and is a signature peak for alcohols.

(4) No, we cannot understand if other minor products alkene is formed, this is because all the alkenes will have same stretching of C=C, =C-H (str, bend) irrespective of their position in the ring. Therefore distinguishing on the basis of IR is not possible.

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