Addition of a Grignard Reagent to which pair of compounds can give tertiary alco

Question

Addition of a Grignard Reagent to which pair of compounds can give tertiary alcohols as products?

a) acid chloride & aldehyde

b) ketone & ester

c) ester & aldehyde

d) ketone & aldehyde

e) formaldehyde & aldehyde

Which substances cannot be reduced with lithium aluminum hydride, LiAlH4 (LiAlH)?

a) ketones

b) alkenes

c) aldehydes

d) carboxylates

e) esters

What is the key step of the generic pinacol rearrangement?

a) hydrogen shift in a carbocation

b) methyl shift in a carbocation

c) methyl shift in a carbanion

d) hydrogen shift in a carbanion

e) hydroxide shift in a carbocation

Which one of the following Grignard reactions is not suited for the preparation of 3-methyl-3-hexanol?

a) 3-hexanone & methylmagnesium bromide

b) pentanal & ethylmagnesium bromide

c) 2-butanone & propyl magnesium bromide

d) 2-pentanone & ethylmagnesium bromide

What is the major product of the following reaction? Ignoring stereochemistry, reaction of 1,3-cyclohcxadicne with Br2 in CCl4 in a 1:1 molar ratio results in which of the following compounds as products? Which of the following is the lowest energy type of transition that occurs in the UV-Vis spectrum of 1,3,5-hexatriene? How many nodes, (other than the node through all p orbitals) arc found in the highest occupied molecular orbital of 1,3,5-hcxatrienc? Which H atom is most susceptible to reaction with and removal by a free-radical? Which of the following descriptions best matches the sequence of events that occurs in the reaction below? What type of mechanism does the reaction below proceed by? Hydration of 1-methylcyclohexene with mercuric acetate would yield primarily which of these?

Explanation / Answer

Ans 1: option b (ketones and esters)

This reaction occurs with a variety of fully substituted 1,2-diols, and can be understood to involve the formation of a carbenium ion intermediate that subsequently undergoes a rearrangement. The first generated intermediate, an %u03B1-hydroxycarbenium ion, rearranges through a 1,2-alkyl shift to produce the carbonyl compound. If two of the substituents form a ring, the Pinacol Rearrangement can constitute a ring-expansion or ring-contraction reaction.

Ans 4: option b (pentanal and ethylmagnesium bromide).

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