The acid D obtained through the following sequence of reactions is:
`C_(2)H_(5)Br overset(Alc. KOH)rarrA overset(Br_(2))underset(C Cl_(4))rarrBoverset(KCN)underset((excees))rarrCoverset(H_(3)O^(+))rarr`

Options

A. Succinic acid
B. Malonic acid
C. Maleic acid
D. Oxalic acid

Answer

To determine the acid D obtained through the given sequence of reactions, let's break down the steps one by one.

### Step 1: Identify the starting compound
The starting compound is ethyl bromide (C₂H₅Br), which can be represented as:
\[ \text{CH}_3\text{CH}_2\text{Br} \]

### Step 2: Reaction with Alcoholic KOH
When ethyl bromide is treated with alcoholic KOH, a dehydrohalogenation reaction occurs, resulting in the elimination of HBr. This leads to the formation of ethene (A):
\[ \text{CH}_3\text{CH}_2\text{Br} \xrightarrow{\text{Alc. KOH}} \text{CH}_2=CH_2 \]

### Step 3: Addition of Bromine
Next, ethene (A) is treated with bromine (Br₂) in carbon tetrachloride (CCl₄), which is a non-polar solvent. This results in the addition of bromine across the double bond, yielding a dibromo compound (B):
\[ \text{CH}_2=CH_2 + \text{Br}_2 \xrightarrow{\text{CCl}_4} \text{CH}_2\text{Br-CH}_2\text{Br} \]

### Step 4: Reaction with KCN
The dibromo compound (B) is then treated with excess KCN. In this step, the cyanide ions (CN⁻) will perform a nucleophilic substitution (SN2 mechanism) on both bromine atoms, replacing them with cyanide groups. This results in a di-cyano compound (C):
\[ \text{CH}_2\text{Br-CH}_2\text{Br} + 2 \text{KCN} \rightarrow \text{CH}_2\text{CN-CH}_2\text{CN} \]

### Step 5: Hydrolysis of the Di-cyano Compound
Finally, the di-cyano compound (C) undergoes hydrolysis when treated with H₃O⁺ (acidic water). This hydrolysis converts the cyanide groups (CN) into carboxylic acid groups (COOH). The resulting compound will be:
\[ \text{CH}_2\text{CN-CH}_2\text{CN} + 2 \text{H}_2\text{O} \xrightarrow{\text{H}_3\text{O}^+} \text{HOOC-CH}_2\text{CH}_2\text{COOH} \]

### Final Structure of Acid D
The final product is succinic acid, which has the structure:
\[ \text{HOOC-CH}_2\text{CH}_2\text{COOH} \]

### Conclusion
Thus, the acid D obtained through the sequence of reactions is **succinic acid**.