Guerbet alcohols, also known as monobranched primary alcohols, are alcohols with a longer hydrocarbon chain than the parent normal alcohol. They are named after French chemist Albert Guerbet who discovered the reaction that allows their synthesis from normal alcohols. Monobranched primary alcohols contain an additional -CH2- group inserted between the hydroxyl group and the hydrocarbon chain. This branching gives them different chemical and physical properties compared to the linear normal alcohols.

Synthesis of Guerbet Alcohols

Monobranched primary alcohols are synthesized from normal alcohols through the Guerbet Alcohols  reaction. In this reaction, two molecules of a primary alcohol undergo dehydration to form an alkene. This alkene then undergoes asymmetric hydrogenation to form a monobranched alcohol. For example, two molecules of butanol react to form 2-butene which is hydrogenated to give 2-ethyl-1-butanol, a C8 monobranched primary alcohol. The overall reaction doubles the carbon chain length while introducing a methyl branching. The reaction requires strong acidic catalysts like sulfuric acid and operates at high temperatures around 150-200°C.

Properties and Applications

The presence of the methyl side chain changes important properties of monobranched primary alcohols compared to linear alcohols. They have higher viscosity and flash point due to steric hindrance from the branching which makes them better solvents. The branching also increases hydrophobicity which is useful in applications such as detergents. Some key properties and applications of common monobranched primary alcohols include:

- 2-Ethylhexanol - Has very low toxicity, is used as a solvent in paints, sealants and personal care products. Also used as an intermediate in plasticizers production.

- Isodecyl Alcohol - Higher flash point than isomers makes it a preferred solvent. Used in cosmetics, coatings, agrochemical and engineering applications.

- Dodecanol - High viscosity and excellent hydrotropy gives superior detergent properties. Used in manufacturing of shampoos, liquid hand soaps and cleaners.

- Tetradecanol - Semi-solid wax with good emulsification properties. Enters in production of cosmetics, creams and oils. Also employed as an emollient and thickening agent.

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