I Paper: I (C) – Organic Chemistry (Gr

Department of Chemistry, Anugrah Memorial College, Gaya

B. Sc. Chemistry (Hons) Part – I Paper: I (C) – Organic Chemistry (Gr. B) Unit I (a): Alcohol Topic: Unsaturated Alcohols Lecture: #1 By: Dr. Rajesh Ranjan Pandey (Assistant Professor)

UNSATURATED ALCHOLS

Contents:  Introduction  Types  Nomenclature  Vinyl Alcohol  Preparation  Properties  PVA  Preparation  Uses

Unsaturated alcohols are those alcohols with carbon chains that contain one or more carbon-carbon double or triple bonds.

Types: Unsaturated monohydric alcohols are of two types according as the -OH group is attached to a carbon which is singly or doubly-linked to another carbon:

Type I: -OH group is attached to a carbon which is doubly-linked to another carbon. eg. vinyl alcohol

Type II: -OH group is attached to a carbon which is singly-linked to another carbon. eg. allyl alcohol

IUPAC Nomenclature:

For eg.

Vinyl Alcohol

Vinyl alcohol, also called ethenol (IUPAC Name), is the simplest enol with the moleclar formula CH₂CHOH. Its also knon as hydroxyethene and hydroxyethylene. It is a labile (unstable) compound that converts to acetaldehyde.

Preparation:

1. From ethylene glycol: Vinyl alcohol can be formed by the pyrolytic elimination of water from ethylene glycol at a temperature of 900 °C and low pressure but it is unstable and its rapidaly converts to acetaldehyde at normal condition. So its generally exist as reaction intermediates.

However, derivatives of vinyl alcohol for e.g. vinyl bromide and vinyl acetate are quite stable.

Properties: 1. Tautomerization of vinyl alcohol to acetaldehyde: Under normal conditions, vinyl alcohol is unstable and its rapidaly converts (tautomerizes) to acetaldehyde:

At room temperature, acetaldehyde is more stable than vinyl alcohol by 42.7 kJ/mol.

poly(vinyl alcohol) [PVOH, PVA, or PVAL]

 a synthetic polymer that is soluble in water

Preparation: PVA is prepared by hydrolysis of polyvinyl acetate.

Uses:  PVA is used in a variety of medical applications because of its biocompatibility, low tendency for protein adhesion, and low toxicity. Specific uses include cartilage replacements, contact lenses, and eye drops.  PVA is used in sizing agents that give greater strength to textile yarns and make paper more resistant to oils and greases.  It is also employed as a component of adhesives and emulsifiers, as a water-soluble protective film, and as a starting material for the preparation of other resins like polyvinyl butyral (PVB) and polyvinyl formal (PVF).

(To be continued…)