Read the following passage given below and answer the question.

Andehydes and ketones undergo nucleophilic addition reactions. A nucleophile attacks the electrophilic carbon atom of polar carbonyl group from perpendicular to plane of \(sp^2\) hybridized orbitals of carbonyl carbon. The hybridization of carbon changes from \(sp^2\) \(sp^3\) and a tetrahedral alkoxide intermediate is formed. This captures \(H^+\) to give neutral product. In carboxylic acids, carbonyl carbon is less electrophilic than carbonyl carbon carbon of aldehydes and ketones.

From the following reactions, identify the reactions which are correctly matched with the names:

Choose the correct answers from the options given below:

A, B, C, E only

The correct answer is option 4. A, B, C, E only.

To verify the reactions given we need to look at each of them carefully:

A. Etard Reaction :

The reaction involves the oxidation of toluene with chromyl chloride \((CrO_2Cl_2)\) in \(CCl_4\). In the case of side chains bigger than \(CH_3\) group the end carbon atom of the chain is oxidized by \(CrO_2Cl_2\) to \(–CHO\) group.

Thus, the reaction given in the question is correct.

B. Rosenmund reduction

Reduction of acid chloride by hydrogenation in the presence of palladium poisoned by barium sulfate gives aldehyde. This is called the Rosenmund reaction. The catalyst is made by reducing a solution of palladium (II) chloride in the presence of barium sulfate. This method cannot produce formaldehyde because formyl chloride is unstable at ambient temperature. Rosenmund reduction is used in the production of saturated fatty aldehyde.

Mechanism:

When hydrogen gas is passed through the acyl chloride in the presence of a rosenmund catalyst, aldehyde, and hydrochloric acid are formed. In this reaction, barium sulfate reduces the activity of palladium and prevents over-reduction.

Thus, the reaction given in the question is correct.

C. Clemmensen reduction:

The Clemmensen Reduction allows the deoxygenation of aldehydes or ketones, to produce the corresponding hydrocarbon.

The substrate must be stable to strong acid. The Clemmensen Reduction is complementary to the Wolff-Kishner Reduction, which is run under strongly basic conditions. Acid-labile molecules should be reduced by the Wolff-Kishner protocol.

Mechanism of the Clemmensen Reduction

In this reaction mineral acid supplies proton to oxygen, whereas metal \(Zn\) supplies an electron pair to the electron deficient carbonyl carbon to form carbanion. This mechanism involves three steps namely (i) formation of carbanion, (ii) elimination of water and (iii) addition of proton

Thus, the reaction given in the question is correct.

D. Balz-Schiemann Reaction:

Balz Schiemann Reaction deals with the preparation and subsequent thermal decomposition of an aromatic fluoborate to give the corresponding aryl fluoride. The reaction gets its name from the German scientists – Günther Schiemann and Günther Balz.

The basic reactants are aromatic amines, nitrous acid, and fluoroboric acid. Aromatic amines undergo diazotization under the influence of nitrous acid. Fluoroboric acid is now added to give rise to the corresponding aryl diazonium salt. Now, this aryl diazonium salt is subjected to heat to undergo thermal decomposition and give the aryl fluoride along with Nitrogen and Boron trifluoride.

Thus, the reaction given in the question is incorrect.

E. Gattermann Koch Reaction:

Gattermann Koch’s reaction mechanism begins with the formation of the reactive species with the help of the acid. The overall aim of the reaction is to attach a formyl group (-CHO group) to an aromatic system. An example of the Gattermann – Koch reaction is given below.

Mechanism:

Gattermann-Koch synthesis is believed to involve electrophilic substitution of the aromatic substrate, the electrophile being the formyl cation.

Thus, the reaction given in the question is correct.

Thus, the correct answer is option 4. A, B, C, E only.