1.Comment about the comparison of the infrared spectra of 2-octanol, 2-bromoocta

Question

1.Comment about the comparison of the infrared spectra of 2-octanol, 2-bromooctane, octenes and trans-2-octene, in regard to presence or absence of peaks in trans-2-octene that support the formation of octenes.

2.What is the solid that forms during the second reaction?

6. If you started with 1-octanol, what would be the expected major product for the first reaction (reaction A) and what would be the expected major product for the second reaction ( reaction B)?

3. Why should trans-2-octene be the most abundant product for the dehydrohalogenation reaction?

Explanation / Answer

1. IR for,

2-octanol :

would show peak at 3200-3600 cm-1 due to OH stretch

peaks 2850-3000 cm-1 for aliphatic C-H stretch

2-bromooctane :

peaks 2850-3000 cm-1 for aliphatic C-H stretch

trans-2-octene :

peak at 3030 cm-1 due to sp2 =C-H stretch [this peak would be absent in both 2-octanol and bromooctane]

peaks 2850-3000 cm-1 for aliphatic C-H stretch

2. The solid product formed in the second step would be the ether, 2-epoxyoctane

3. With 1-ctanol under acidic conditons, the expected product would be 2-bromooctane in the first step (A)

In step B the expected product from the E2 elimination of 2-bromooctane would be, 2-octene

4. Trans-octene being the least sterically hindered is the most stable (lowest energy) compound of the elimination reaction and thus is the major product formed in this case.

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