Question

When an acyl chloride is heated with $Na$ salt of a carboxylic acid, the product is :
A.) an aldehyde
B.) an alkene
C.) an anhydride
D.) an ester

Answer 1

Hint: This question can be solved by the concept of nucleophilic substitution reaction. These are those reactions in which an electrophile is replaced by a nucleophile. We have to see in this question which one acts as electrophile and which acts as nucleophile.

Complete step by step answer:
To solve this question, first we will understand the concept of nucleophilic substitution reaction.
Nucleophilic substitution reactions are those reactions in which an electrophile is replaced by a nucleophile.
Here, nucleophile means that reactant which provides a pair of electrons to form a new covalent bond and electrophile is a reactant that accepts a pair of electrons to form a new covalent bond.
Nucleophilic substitution reactions are also called the $SN$ reaction. Here $S$ stands for substitution and $N$ refers to nucleophilic.
In the compounds that are given in question, acyl chloride is a compound that contains $ - COCl$ group in it. It is generally represented as $R - COCl$.
And $Na$ salt of carboxylic acid can be written as $RCOONa$.
Here $RC{O^ - }$ of acyl group acts as a nucleophile and it will replace the electrophile that is present as $N{a^ + }$ in $RCOONa$. So the reaction can be shown as:
$RCOONa + R'COCl \to RCO - O - CO - R' + NaCl$
Thus, we can see that when sodium salt of carboxylic acid reacts with acyl chloride then anhydride is obtained.
Hence, option C.) is the correct answer.

Note:
Remember that generally the nucleophiles are negatively charged and the electrophile are positively charged. But there may be such cases when electrophile and nucleophile are neutral species such as: $AlCl_3$ , $BF_3$ are neutral electrophiles and $NH_3$ , $RNH_2$ are neutral nucleophiles.