Chapter 21, Problem 21.45P

Interpretation Introduction

(a)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Sodiumborohydride is a metal reducing agent. It reduces ketones and aldehyde into secondary alcohols and primary alcohols respectively.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

In the presence of sodium borohydride and methanol, phenylacetaldehyde gets reduced to $2$-phenylethanol. The corresponding chemical reaction is shown below.

Figure 1

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 1.

Interpretation Introduction

(b)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Lithium aluminum hydride is a strong reducing agent. Treatment of carbonyl compounds with lithium aluminum hydride followed by water yields alcohols. It reduces aldehyde into primary alcohol.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

In the presence of lithium aluminium hydride followed by hydrolysis, phenylacetaldehyde gets reduced to $2$-phenylethanol. The corresponding chemical reaction is shown below.

Figure 2

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 2.

Interpretation Introduction

(c)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Grignard reagents are organometallic compounds which are prepared using alkyl halides in presence of magnesium metal in dry ether. These reagents act as strong nucleophiles and bases.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

In the presence of Grignard reagent followed by hydrolysis, phenylacetaldehyde forms primary alcohol. The corresponding chemical reaction is shown below.

Figure 3

The product formed is $1$-phenylpropan-$2$-ol.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 3.

Interpretation Introduction

(d)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Nucleophilic addition reaction is a type of organic reaction in which the nucleophile is added to an electrophilic site. In case of carbonyl compounds, the carbonyl carbon acts as an electrophilic site.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with sodium cyanide followed by protonation to form $2$-hydroxy-$3$-phenylpropanenitrile. The corresponding chemical reaction is shown below.

Figure 4

Conclusion

Interpretation Introduction

(e)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

In Wittig reaction, aldehyde can be directly converted to alkene using triphenyl phosphonium ylide. The geometry of the alkene formed, depends on the stability of the ylides.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde on reaction with Wittig reagent ${\text{Ph}}_{\text{3}}\text{P}={\text{CHCH}}_{\text{3}}$ yields alkene. The corresponding chemical reaction is shown below.

Figure 5

The products formed are $(E)\text{-but-2-en-1-ylbenzene}$ and $(Z)\text{-but-2-en-1-ylbenzene}$.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 5.

Interpretation Introduction

(f)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Aldehyde or ketone on reaction with primary amine forms imine. Imine is also known as Schiff base. The nucleophilic attack of primary amine on carbonyl carbon results in the formation of intermediate carbinolamine. This intermediate loses water to form an imine.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with ${{\text{(CH}}_{\text{3}}\text{)}}_2{\text{CHNH}}_{\text{2}}$ in presence of mild acid to form imine. The corresponding reaction is as follows,

Figure 6

The product formed is $N$-($2$-phenylethylidene) propan-$2$-amine.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 6.

Interpretation Introduction

(g)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Aldehyde or ketone on reaction with secondary amine forms enamine. The nucleophilic attack of secondary amine on carbonyl carbon results in the formation of intermediate carbinolamine. This intermediate loses water to form an enamine. In this case, the elimination occurs across two adjacent carbon atoms to form new carbon-carbon double bond.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with ${{\text{(CH}}_{\text{3}}{\text{CH}}_2\text{)}}_2\text{NH}$ in presence of mild acid to form enamine. The corresponding reaction is as follows,

Figure 7

The products formed are $(E)\text{-}N,N$-diethyl-$\text{2}$-phenylethanamine and $(Z)\text{-}N,N$-diethyl-$\text{2}$-phenylethanamine.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 7.

Interpretation Introduction

(h)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Aldehydes or ketones on reaction with one equivalent of alcohol form hemiacetal and on reaction with two equivalents of alcohol it forms acetals. This is nucleophilic addition reaction. These reactions take place in presence of acids.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with excess of ethanol in presence of acid to form acetal. The corresponding reaction is as follows,

Figure 8

The product formed is ($2,2$-diethoxyethyl) benzene.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 8.

Interpretation Introduction

(i)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Aldehyde or ketone on reaction with secondary amine forms enamine. The nucleophilic attack of secondary amine on carbonyl carbon results in the formation of intermediate carbinolamine. This intermediate loses water to form an enamine. In this case the elimination occurs across two adjacent carbon atoms to form new carbon-carbon double bond.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with piperidine in presence of mild acid to form E and Z isomers of $1$-styrlpiperidine. The corresponding reaction is as follows,

Figure 9

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 9.

Interpretation Introduction

(j)

Interpretation:

The product formed on treatment of phenylacetaldehyde with given reagent is to be predicted.

Concept introduction:

Aldehydes or ketones on reaction with one equivalent of alcohol form hemiacetal and on reaction with two equivalents of alcohol it forms acetals. This is nucleophilic addition reaction. These reactions take place in presence of acids.

Answer to Problem 21.45P

The product formed on treatment of phenylacetaldehyde with given reagent is,

Explanation of Solution

Phenylacetaldehyde reacts with ethane-$1,2$-diol in presence of acid to form cyclic acetal. The corresponding reaction is as follows,

Figure 10

The product formed is $2$-benzyl-$1,3$-dioxolane.

Conclusion

The product formed on treatment of phenylacetaldehyde with given reagent is shown in figure 10.