in-an-organic-chemistry-lab-experiment-2-methyl-3-hexanone-is-reacted-with-allyl

Question

In an organic chemistry lab experiment, 2-methyl-3-hexanone is reacted with allyl magnesium bromide yielding a tertiary alcohol. The ¹H NMR of 2-methyl-3-hexanone shows that the two methyl groups are equivalent indicated by a one doublet peak. On the other hand, the product (a racemic mixture), gives two different 3H doublets.
(i) Along the C2–C3 axis, show a Newman projection of the product.
(ii) Why do the methyl groups of the product show different signals? What is the term used to describe such groups?

(i) Along the C2–C3 axis, show a Newman projection of the product.

(ii) Why do the methyl groups of the product show different signals? What is the term used to describe such groups?

Accepted Answer

(i)

(ii) The methyl groups of the product show different signals because of the creation of a new chiral center affecting nearby protons. These methyl groups are diastereotopic.

Answer

(i)

(ii) The methyl groups of the product show different signals because of the different electronegative substituents. These methyl groups are heterotopic.

Answer

(i)

(ii) The methyl groups of the product show different signals because of the formation of chemically equivalent environments. These methyl groups are homotopic.

Answer

(i)

(ii) The methyl groups of the product show different signals because of the resonance stabilization by adjacent groups. These methyl groups are enantiotopic.

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