Types of Alcohol: Primary, Secondary, and Tertiary Alcohol

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The organic compounds that are characterized by the presence of either one or more hydroxyl groups are known as alcohol. The hydroxyl group in alcohol is linked to the Carbon atom of the hydrocarbon chain or the alkyl group. They are classified further into primary alcohol, secondary alcohol, and tertiary alcohol. Alcohols also have certain day-to-day applications. For instance, ethanol generally acts as a fuel. In this article, we will have a look at alcohol, its classification, and its uses and types.

Table of Content

What is Alcohol?
Uses of Alcohol
Common Types of Alcohol
Classification of Alcohol
Things to Remember
Sample Questions

Read Also: Carbon and Its Compounds

What is Alcohol?

Alcohol is a derivative of water (H₂O) that has one, two, or more hydroxyl groups that are attached to a carbon atom of a hydrocarbon chain (an alkyl group). It is one of the most common organic compounds used in sweeteners, fragrances, and medicine.

Alcohol

Pure alcohol is a colorless liquid that becomes solid at room temperature. Low molecular weight alcohol is soluble in water. As molecular weight increases, so does the solubility of alcohol in water. Hence, its boiling point, vapor pressure, density, and viscosity also increase.

Elimination Reaction	Combustion Reaction
Versatile Nature of Carbon	Soaps and Detergents

Uses of Alcohol

Ethanol is the alcohol used in alcoholic drinks. It can be used as an industrial methylated spirit where methanol is used very little in quantity as it can be dangerous.
It is used as fuel to produce carbon dioxide and water by the process of fermentation. Whereas methanol burns carbon dioxide and water to facilitate combustion.
Alcohol is an organic compound used as a solvent that is insoluble in water.
It can be used to lower the level of sugar.
Alcohol is used as a preservative in laboratories.

Uses of Alcohol

Common Types of Alcohol

Methanol(CH₃OH):Methanol is non-drinking alcohol, it can also be called wood alcohol and methyl alcohol. Methanol is mainly used as fuel and as a solvent. It is flammable, volatile, and poisonous to humans, unlike ethanol. It can be dangerous sometimes as it can cause blindness or death if the quantity exceeds the limit of 50 ml.

Methanol

Ethanol: The substance ethanol is used to make drugs, plastics, lacquers, paints, plasticizers, and cosmetics. It is used in medicine to treat infections and as an antidote for ethylene glycol or methanol poisoning. Ethanol is observed to produce acetaldehyde in the body.

CH₃CH₂OH

Ethanol

Propanol: Alcohols with 3 carbon chains are called propanol(C3H7OH). Propanol is used to treat tremors, angina (chest ache), hypertension (excessive blood stress), coronary heart rhythm disorders, and different coronary heart or circulatory situations. It can also prevent heart attacks, and it reduces migraine headache severity.

CH₃CH₂CH₂OH

Propanol

Ethylene glycol: The substance ethylene glycol is a liquid that can absorb water. Generally, ethylene glycol is used in antifreeze and de-icing solutions for automobiles, subways, boats, and airplanes. This solution also has traces in ballpoint inks, hydraulic brake fluids, printing shops, and stamp pad inks. Despite its colorlessness and odorless nature, ethylene glycol has a sweet taste.

OH-CH₂-CH₂-OH

Ethylene Glycol

Propylene glycol: This material absorbs excess water and maintains moisture in medicines, cosmetics, or food products. Colors and flavors in food are made from it, and it is used in paint and plastics manufacturing. A variety of propylene glycol applications include creating artificial smoke and fog for theatrical and training purposes. As a viscous, colorless liquid, propylene glycol is odorless and tasteless except for a little sweetness.

Propylene Glycol

Classification of Alcohol

The classification of alcohol is based on –

The number of the hydroxyl group.

Monohydric Alcohol: One hydroxyl group present. Example: phenol
Dihydric Alcohol: Two hydroxyl groups present. Example: 1,2-benzenediol.
Trihydric Alcohol: Three hydroxyl groups present. Example: glycerol.

The number of alkyl groups paired to carbon-bearing the OH group.

Classification of Alcohol

Primary Alcohol: Those alcohols whose carbon atom is embedded within a single alkyl group (OH) are primary alcohols. Methanol (propanol), ethanol, etc., are a few of these primary alcohols. Regardless of the complexity of the alkyl chain, there is no correlation between the class of primary alcohols and this chain. There can only be one interaction between an -OH group and an alkyl group for alcohol to be called primary.

Primary Alcohol

Primary Alcohol

Secondary Alcohol: It is represented as 2° alcohol. Secondary alcohol is one with two alkyl groups attached to each side of the carbon atom of the hydroxyl group. The two alkyl radical groups could also be either structurally identical or may be completely different. Propanol and butanol are examples of secondary alcohol.

Secondary Alcohol

Secondary Alcohol

Tertiary Alcohol: Tertiary alcohols are the units that feature hydroxyl radicals hooked up to the atom that is connected to 3-radical groups. Its physical properties chiefly rely upon its structures. The presence of this –OH cluster permits the alcohols within to form H-bonds with their neighboring atoms. The bonds make the boiling points of these alcohols above its alkanes.

Tertiary Alcohol

Tertiary Alcohol

On the basis of the hybridization of carbon that is hydroxylated

Compounds with sp3-OH bond
- Allylic Alcohol: Hydroxyl group is attached to the sp3 hybridized carbon which is next to a double carbon-carbon bond.
- Benzylic Alcohol: Hydroxyl group is attached to the sp3 hybridized carbon in an aromatic ring.
Compounds with sp2-OH bond
- Vinylic Alcohol: Hydroxyl group is attached to the carbon of a double carbon-carbon bond.
- Phenols: Hydroxyl group is attached to a carbon atom in the benzene ring.

Isomerism	Organic Compounds
Tetravalency of Carbon	Cis-Trans Isomers

Things to Remember

Alcohol is an organic compound attached to a hydrocarbon chain (carbon atom of an alkyl group) with one or more hydroxyl groups.
It is used as a synthetic intermediate in cleansers, cosmetics, fuel, alcoholic beverages, etc.
Primary alcohol (1° alcohol) whose carbon atom is embedded in one alkyl group. That is only one interaction takes place between the hydroxyl group and alkyl group.
Similarly, in secondary and tertiary groups, the carbon atoms are embedded in two and three alkyl groups respectively.
Pure alcohol is a colorless liquid that becomes solid at room temperature.
Low molecular weight alcohol is soluble in water. As molecular weight increases, so does the solubility of alcohol in water.

Sample Questions

Ques. Explain how glucose is broken down in the shortage or the absence of oxygen. (3 marks)

Ans. There are two approaches to an anaerobic breakdown of glucose.

In both cases, a glucose molecule is broken down into pyruvate in the cytoplasm.
The anaerobic breakdown in bacteria is called fermentation.
During fermentation, the pyruvate is broken down to result in the formation of carbon dioxide and ethyl alcohol.
When there is a lack of oxygen in our muscle cells, pyruvate is broken down into lactic acid.

Ques. What are

alkanes,
alkenes, and
alkynes

Which of them is C₄H₁₀? (3 marks)

Ans. Alkanes - Saturated hydrocarbon with a single bond between carbon-carbon atoms (C-C).

General formula \(C_nH_{2n+2}\)

Alkenes - Unsaturated hydrocarbon with a double bond between carbon-carbon atoms (C=C).

General formula \(C_nH_{2n}\)

Alkyne - Unsaturated hydrocarbon with a triple bond between carbon-carbon atoms.

General formula \(C_nH_{2n-2}\)

C₄H₁₀is an Alkane.

Ques. Write the structural formula of ethanol. What is the result of heating the substance with excessive conc. H₂SO₄ at 443K? What would be the chemical equation in this reaction? (3 marks)

Ans. Formula of ethanol
H H
H-C-C-O-H
H H
when ethanol is heated more than H₂SO₄ at 443K, dehydration takes place and ethanol is converted into ethane, therefore at 443K
C₂H₅OH +H₂SO₄(EXCESS) → C₂H₄ + H₂O
Thus, in this reaction, the role of H2SO4 is of a dehydrating agent.

Warner’s Theory of Coordination Compounds	Nomenclature of Coordination Compounds
Isomerism in Coordination Compounds	Bonding in Metal Carbonyls

Ques. Name the alcohol that contains three carbon atoms. State its structure. (1 marks)

Ans. Propanol(C₃H₇OH) is an alcohol with three carbon atoms. Its structure is CH₃-CH₂-CH₂-OH.

Ques. Write down the chemical equation for the reaction between ethanoic acid and the following:

Sodium
Sodium hydroxide
Ethanol.

Mention one main product each of all the three reactions. (5 marks)

Ans. (a) When ethanoic acid reacts with sodium, the equation will be:

CH₃COOH + 2 Na → 2CH₃COONa + H₂

Sodium Ethanoate will be formed as the main product of each reaction.

(b) When ethanoic acid reacts with sodium hydroxide, the equation will be:

2CH₃COOH + NaOH → 2 CH₃COONa + H₂O

The main product formed will be sodium ethanoate.

(c) When ethanoic acid reacts with ethanol, the chemical equation will be:

2CH₃COOH + C₂H₅OH (conc. H₂SO₄)→ CH₃COOC₂H₅ + H₂O

Ethyl Ethanoate will be formed as the main product.

Ques. An aldehyde, as well as a ketone, may be represented through the same molecular components, say C₃H₆O. Write their structures and name them. Find the relation between an aldehyde and a ketone. (3 marks)

Ans. C₃H₆O represents aldehyde and ketone with the same molecular formula which are propanal and propanone respectively.

Aldehyde - Propanal - CH₃CH₂CHO

Ketone - Propanone - CH₃COCH₃

These two carbon compounds are called functional isomers. They do not have the same physical properties since their functional group is different.

When hydrogen is present on one side of the C=O group and another side is R, (RCHO), then it is an aldehyde group. When R is present on both sides of the C=O group, then it is a ketone.

Propanol and Propanone