Types of Alcohol in Chemistry
Types of alcohol uses for the manufacture of drinks or beer, vodka, brandy is ethyl alcohol or ethanol but monohydric, polyhydric, aromatic, and aliphatic alcohols are used in different alcoholic content like food beverages and drug preparation. Alcohol is the isomers of ether or hydroxyl derivative of hydrocarbon prepared from alkene with specific heat and dilute sulfuric acid under pressure.
Properties of alcohol
The lower members of alcohol are liquids and lees volatile due to association through hydrogen bonding extending over a chain of molecules. The higher members are solid and almost orderless. The lower alcohols are very soluble in water and solubility diminishes as molecular weight increases because the oxygen atom of the hydroxyl group forms hydrogen bonding with water molecules.
Infrared spectrum studies of hydroxyl groups in alcohol show they absorbed electromagnetic spectrum radiation with the frequency from 3650 to 3580 cm-1 and this is true only if there is no hydrogen bonding. Therefore, intermolecular hydrogen bonding in alcohols produces absorption in the region from 3550 to 3230 cm-1.
Acidic nature of alcohol
Alcohol withdrawal hydrogen atom by the action of metals shows acid properties but they do not affect the pH scale of the water solution since they are weaker acid than water. Therefore, the alkoxides beings hydrolyzed by water, and for this reason, ethoxide is the stronger base than the hydroxide ion.
Classification of alcohol
According to the number of functional or alcoholic groups, these organic compounds in chemistry are classified as, monohydric, dihydric, trihydric, polyhydric alcohol. But other types of classification of alcohol are given according to the attached alcoholic group to the aromatic or aliphatic compounds or hydrocarbon.
Monohydric alcohols are organic compounds that contain one alcoholic or hydroxyl group. Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, phenol are examples of monohydric alcohols. They are commonly two types, aromatic and aliphatic alcohol.
General formula of monohydric alcohol
The monohydric alcohols are the simplest with the general molecular formula, CnH2n+2O or CnH2n+1OH. Monohydric alcohols are further classified according to structural formula as primary, secondary, and tertiary alcohol. Hence the classification is based on the position of the alcoholic group attached to the alkyl. If the alcoholic group is attached to the alpha, beta, and gamma carbon atoms, then these alcohols are known as primary secondary, and tertiary respectively.
Dihydric and trihydric alcohol contain two or three alcoholic or hydroxyl groups. But the alcohols contain four or more than four alcoholic groups called polyhydric alcohols. Ethylene glycol, trimethylene glycol, pentamethylene glycol, isobutene glycol are examples of such types of alcohols.
Aromatic alcohols are the class of organic compounds containing an alcoholic or hydroxyl group in a side chain or directly to the hydrocarbon. It may be regarded as aryl derivatives of the aliphatic alcohols. Aromatic alcohols may be classified as primary, secondary, and tertiary alcohols. The methods of preparation of this type of alcohol are similar to the aliphatic alcohols.
Types of aromatic alcohol
Aromatic alcohols are also classified as monohydric, dihydric, trihydric, and polyhydric phenols, according to the hydroxyl group attached to the benzene ring. Phenol, catechol (o-dihydroxybenzene), Resorcinol (m-dihydroxybenzene), quinol (p-dihydroxy benzene ) are examples of these types of alcohols.
Classification of alcohol is given according to the attached alcoholic group to the aromatic or aliphatic hydrocarbon. Hence these organic compounds are named aliphatic and aromatic alcohols. Aliphatic alcohols are compounds containing hydroxyl groups in the side chain of the alkyl group.
Types of aliphatic alcohol
- Methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutanol, etc are examples of monohydric alcohols because these contain only one hydroxyl group.
- But ethylene glycol, trimethylene glycol, pentamethylene glycol, isobutene glycol are dihydric types of aliphatic alcohols. These chemicals contain two alcoholic groups.
- The only important trihydric aliphatic organic compound is glycerol or propane-1-2-2-triol because these contain three alcoholic groups. Glycerol occurs in almost all animals and vegetable oils.
- D-sorbitol, D-mannitol, and dulcitol are the polyhydric aliphatic alcohols that occur naturally contain more than three hydroxyl groups.
Chemical names and formula
Different types of simpler monohydric alcohols are known by their trivial names for learning chemistry. This type of naming is obtained from the alcohol formula which is the chemical derivative of the alkanes or paraffin like methane, ethane, propane, etc attached to the hydroxyl or alcoholic group.
|Examples of alcohol|
Other types of naming by considering the alcohols as the derivative of methanol. For example, CH3CH2CH3OH, ethyl methanol, CH3CH2CH(OH)CH3, methyl ethyl methanol.
Uses of Alcohol
- Alcohols are the commercially essential organic chemical compounds and common types of alcohol content used mainly in alcoholic wine beverages like vodka, beer, whisky, etc.
- It is used as a solvent for paints, varnishes, shellac, celluloid, and cement plant.
- When ethyl alcohol or ethanol mixed with small amounts of methanol forms methylated spirit which mixture used as an automobile antifreeze mixture, remove ink from various kinds of surfaces.
- Alcohol uses for manufacturing dyes and antibiotics drugs, perfumes, etc, and ethanol is also used as an alternate fuel for the motor vehicle or energy generation (renewable energy) process. Common alcohols like Phenol, methanol, ethanol are used as an antiseptic, alcohol-based hand sanitizer, and preparation of antibiotics drugs or bakelite.
Methods of preparation of alcohols
Hydrolysis of alkyl halides
Alcohols may be prepared by hydrolysis of an alkyl halide with silver oxide suspended in water. It is also prepared by hydrolysis of esters with alkali. This method is important for the preparation of tertiary alcohols.
Bouveault Blanc reduction
Reduction of the aldehydes, ketones, or esters by excess sodium in ethanol or n-butanol gives alcohols. The process is called Bouveault Blanc reduction.
Alcohols may be prepared by heating ethers with dilute sulfuric acid under pressure. For example, diethyl ether forms ethanol.
Hydration of alkenes
Alkenes may be hydrated to alcohols by absorption in concentrated sulfuric acid followed by hydrolysis of the alkyl sulfate with water.
Hydroboration of alkenes
Alkenes react rapidly with diborane (B2H6) in ether or THF at room temperature producing trialkyl boranes. Trialkyl boranes on oxidation with alkaline hydrogen peroxide produces primary alcohols.
Alcohol from Grignard reagent
Primary, secondary, and tertiary alcohols may be prepared from appropriate carbonyl compounds by the action of the Grignard reagent.
Yeast fermentation process
Fermentation in the environment is the earliest method for the preparation of ethyl alcohol by the chemical catalyst and uses for the manufacture of different types of drinks brands like beer, wine, whisky, and brandy. The common materials used for these chemical equilibrium reactions are wheat, barley, or potato. The mashed materials boil at 50 °C for one hour. But the melt contains the enzyme diastase effects on starch to convert maltose and sugar by hydrolysis in the alcohol preparation process, 2(C6H10O5)n + nH2O → nC12H22O11.
The liquid is cooled to 300 °C and fermented with yeast for 1-3 days. Yeast contains various enzymes, among which maltase converts maltose into glucose and zymase. But zymase further converted glucose into ethanol (C2H5OH). The carbon dioxide gas is recovered and sold as a by-product. The fermented liquor contains 6 -10 percent alcohol used for the manufacture of wine, beer, brandy, or other types of food beverage.