Chapter 17, Problem 17.55P

Interpretation Introduction

(a)

Interpretation:

The complete mechanism for the reaction between the given Wittig reagent and benzaldehyde is to be drawn.

Concept introduction:

Wittig reactions generate the carbon double($\text{C = C}$) bond by joining two carbon-containing groups - one from the Wittig reagent and the second from the aldehyde or ketone. In a Wittig reaction, the carbonyl ($\text{C=O}$) bond of aldehyde or ketone is converted o a ($\text{C = C}$) bond. In step one, the negatively charged C atom from the Wittig reagent attacks the aldehyde and produces a betaine, that is, the species in which negative charge is present on O atom and a positive charge on P atom. In step two, a bond is formed between a positively charged P atom and negatively charged O atom. This results in an oxaphosphetane that contains a four-membered ring. Due to the ring strain, strainoxaphosphetane converts to alkene and triphenylphosphine oxide in the final step.

Interpretation Introduction

(b)

Interpretation:

The complete mechanism for the reaction between given Wittig reagent and benzaldehyde is to be drawn.

Concept introduction:

Wittig reactions generate the carbon double($\text{C = C}$) bond by joining the two carbon-containing groups - one from the Wittig reagent and the second from the aldehyde or ketone. In a Wittig reaction, the carbonyl ($\text{C=O}$) bond of aldehyde or ketone is converted to a ($\text{C = C}$) bond. In step one, the negatively charged C atom from the Wittig reagent attacks the aldehyde and produces a betaine, that is species in which negative charge is present on O atom and a positive charge is on P atom. In step two, a bond is formed between a positively charged P atom and negatively charged O atom. This results in an oxaphosphetane that contains a four-membered ring. Due to the ring strain oxaphosphetane converts into the alkene and triphenylphosphine oxide in the final step.

Interpretation Introduction

(c)

Interpretation:

The complete mechanism for the reaction between given Wittig reagent and benzaldehyde is to be drawn.

Concept introduction:

Wittig reactions generate the carbon double($\text{C = C}$) bond by joining the two carbon-containing groups - one from the Wittig reagent and the second from the aldehyde or ketone. In a Wittig reaction, the carbonyl ($\text{C=O}$) bond of aldehyde or ketone is converted to a ($\text{C = C}$) bond. In step one, the negatively charged C atom from the Wittig reagent attacks on the aldehyde and produces a betaine, that is species in which negative charge is present on O atom and a positive charge on P atom. In step two, a bond is formed between a positively charged P atom and negatively charged O atom. This results in an oxaphosphetane that contains a four-membered ring. Due to the ring strain, oxaphosphetane converts into the alkene and triphenylphosphine oxide in the final step.