Q35E - Organic Chemistry (Mcmurry)

Question

2-Ethyl-1-hexanol, used in the synthesis of di(2-ethylhexyl) phthalate plasticizer, is made commercially from butanal. Show the likely synthesis route.

Step-by-Step Solution

Answer

The likely synthesis route for the synthesis of 2-Ethyl-1-hexanol is initiated by aldol self-condensation of butanal, followed by dehydration and reduction give our desired product.

Step 1: Aldol-self Condensation

Aldol Condensation is also known as Aldol-self condensation because in this reaction two of the same molecules or carbonyl compounds are condensed. It occurs in aldehyde having α-hydrogen with the dilute base to give β-hydroxy aldehyde called aldols.

If the condensation reactions occur between two different carbonyl compounds then it is known as crossed aldol condensation.

Step 2: Plasticizer

Plasticizers are defined as small organic molecules that act as lubricants between chains and are usually added to thermoplastics to keep them from becoming brittle at room temperature.

An example is a poly (vinyl chloride), which is brittle when pure but becomes supple and pliable when a plasticizer is added.

Dialkyl phthalates such as di (2-ethylhexyl) phthalate (generally called dioctyl phthalate) are commonly used as plasticizers, although questions about their safety have been raised.

Step 3: Synthesis of 2-Ethyl-1-hexanol

The likely synthesis route for the synthesis of 2-Ethyl-1-hexanol is initiated by aldol self-condensation of butanal, followed by dehydration with NaBH4 in the presence of hydronium ion gives 2-ethylhex-2-en-1-ol which on further undergoes reduction with a Palladium catalyst to gives our desired product as shown below: