Alcohols, Phenols Class 12 Notes | EduRev

Chemistry for JEE

Class 12 : Alcohols, Phenols Class 12 Notes | EduRev

The document Alcohols, Phenols Class 12 Notes | EduRev is a part of the Class 12 Course Chemistry for JEE.
All you need of Class 12 at this link: Class 12

Alcohols

Alcohols, Phenols Class 12 Notes | EduRevEthanol

Physical Properties

(1) Boiling point : 

(a) Alcohols show an increase in boiling point with an increase in molecular weight amongst homologues.

(b) Alcohols have a higher boiling point than hydrocarbons of the same molecular weight. The reason for the higher boiling point is the intermolecular H-bonding present in alcohols.


Alcohols, Phenols Class 12 Notes | EduRevEthanol has a higher Boiling Point than Ethane.



Alcohols, Phenols Class 12 Notes | EduRevHydrogen Bonding in Ethanol


(2) Solubility in water :

As molecular weight increases solubility in water decreases. The lower alcohols are miscible with water. This is due to intermolecular hydrogen bonding between alcohol and water molecules.

Alcohols, Phenols Class 12 Notes | EduRev

Intermolecular H bond between water & alcohol molecules.

Alcohols, Phenols Class 12 Notes | EduRevTable showing Solubility of various Alcohols


Preparation of Alcohols(1) From Alkenes (a) By acid-catalyzed hydration of alkenes: Formation of carbocation intermediate (Markovnikov addition, rearrangement possible).

Alcohols, Phenols Class 12 Notes | EduRevThe reaction of Alkenes with Acids follow Markovnikov's Rule

General reaction:  

Alcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRev     


(b) By Oxymercuration - Demercuration process :

(1) Oxymercuration involves an electrophilic attack on the double bond by the positively charged mercury species. The product is a mercurinium ion, an organometallic cation containing a three-membered ring.

Alcohols, Phenols Class 12 Notes | EduRev

(2) In the second step, water from the solvent attacks the mercurinium ion to give (after deprotonation) organomercurial alcohol. 

(3) The third step is demercuration to remove the Hg. Sodium borohydride (NaBH4, a reducing agent) replaces the mercuric acetate fragment with hydrogen.


General reaction:

Alcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRev  + OH- + NaBH4Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(c) By Hydroboration-oxidation process: 

Alcohols, Phenols Class 12 Notes | EduRev


(Forms anti-Markovnikov alcohol, no rearrangement).

General reaction: R-Ch=CH2Alcohols, Phenols Class 12 Notes | EduRevR-CH2-CH2-OH

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

Ex. Give the major product of the following reaction:

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Ans. Major product is

(a) Alcohols, Phenols Class 12 Notes | EduRev
because 3o carbocation is more stable.

(b) Alcohols, Phenols Class 12 Notes | EduRev

(c) Alcohols, Phenols Class 12 Notes | EduRev


(2) From Alkyl Halides 

By nucleophilic substitution reactions.

(a) By SN2 mechanism (second-order substitution)

It is given by primary (and some secondary) halides.

General reaction: R-CH2-Br Alcohols, Phenols Class 12 Notes | EduRev R-CH2-OH

e.g. (CH3)2CHCH2CH 2-Br Alcohols, Phenols Class 12 Notes | EduRev (CH3)2CHCH2CH 2- OH

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(b) By SN1 mechanism (first-order substitution)It is given by tertiary and some secondary halides. 

General reaction : Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(3) From Grignard's reagent. 

(a) From air:

A Grignard reagent may be used to synthesize an alcohol by treating it with dry oxygen and decomposing the product with acid :

General reaction RMgX Alcohols, Phenols Class 12 Notes | EduRev RO2MgX Alcohols, Phenols Class 12 Notes | EduRev 2ROMgX Alcohols, Phenols Class 12 Notes | EduRev 2ROH

e.g. C2H5MgBrAlcohols, Phenols Class 12 Notes | EduRevC2H5O2 MgXAlcohols, Phenols Class 12 Notes | EduRev2C2H5OMgX Alcohols, Phenols Class 12 Notes | EduRev2C2H5OH MgBr(OH)


(b) From ethylene oxide:

The addition of Grignard reagent to ethylene oxide gives primary alcohol (with two carbon atoms added).

General reaction Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev RCH2CH2OMgX Alcohols, Phenols Class 12 Notes | EduRev RCH2CH2OH MgX(OH)

e.g. Alcohols, Phenols Class 12 Notes | EduRev C2H5MgBr Alcohols, Phenols Class 12 Notes | EduRev C2H5CH2CH2 OMgX Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev MgBr(OH)

(c) From carbonyl compounds: Nucleophilic addition to the carbonyl groups by Grignard's reagent.

Alcohols, Phenols Class 12 Notes | EduRev

General reactionAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev Mg(OH)X

 

(i) Addition of formaldehyde gives primary alcohol. 

General reactionAlcohols, Phenols Class 12 Notes | EduRev= O RMgX Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevRCH2-OH


(ii) Addition to an aldehyde (other than formaldehyde) gives secondary alcohol. 

General reaction:

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev (sec-alcohol)

 

e.g.Alcohols, Phenols Class 12 Notes | EduRev +  Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

(iii) Addition to a ketone gives tertiary alcohol. 

General reaction:

 Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g. CH3CH2MgCl +  Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(iv) Addition to an acid halide or an ester gives tertiary alcohol.

Esters on treatment with Grignard's reagent first form ketones which then react with the second molecule of Grignard's reagent and form tertiary alcohol.

General reaction:

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

(4) By reduction of carbonyl compounds.(a) Catalytic hydrogenation of aldehydes and ketones. 

Alcohols, Phenols Class 12 Notes | EduRev


Alcohols, Phenols Class 12 Notes | EduRev

General reaction: 

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g. CH3CHO + 2H Alcohols, Phenols Class 12 Notes | EduRev CH3CH2OH

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev CH3CH2CH2OH

Alcohols, Phenols Class 12 Notes | EduRev + 4H Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

(b) Lithium aluminium hydride reduction of aldehydes and ketones.

General reaction:

(i) Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

(ii) Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

(iii) RCOOH+ 4H Alcohols, Phenols Class 12 Notes | EduRev RCH2OH + H2O

(iv) Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev RCH2OH+ HCl

(v) Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev R-CH2OH +R'OH

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev CH3CH2OH

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev C2H5CH2OH +HCl

 

(c) By NaBH4 (sodium borohydride) 

It is insoluble in ether and is used in an aqueous ethanolic solution to reduce carbonyl compounds. It does not reduce esters and acids.

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev R-CH2-OH

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevCH=CHCHO +4H Alcohols, Phenols Class 12 Notes | EduRev CH3CH=CHCH2OH

(ii) Reduction of a ketone gives secondary alcohol.

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(d) Bouveault-Blanc reduction

Alcohols, Phenols Class 12 Notes | EduRev

The reduction of aldehydes, ketones or esters by means of excess of sodium and ethanol or n-butanol as the reducing agent.

General reaction:

(i) Aldehyde  RCHO Alcohols, Phenols Class 12 Notes | EduRevRCH2OH

(ii) Esters  R'CO2R'' Alcohols, Phenols Class 12 Notes | EduRevR'CH2OH R''OH

(iii) Ketones  R2CO Alcohols, Phenols Class 12 Notes | EduRevR2CHOH

The Bouveault-Blanc reduction is believed to occur in steps involving transfer of one electron at a time.

Mechanism:

Alcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRev

e.g. CH3CHO +2H Alcohols, Phenols Class 12 Notes | EduRevCH3CH2OH

CH3COOC2H5 +4HAlcohols, Phenols Class 12 Notes | EduRev2CH3CH2OH

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Ex. Identify (X) in the following reaction:

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevX

Ans.Alcohols, Phenols Class 12 Notes | EduRev

 

Ex. What are the product A, B, C, D and E in the following reactions?

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevA Alcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevD Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevE

Ans. A : Alcohols, Phenols Class 12 Notes | EduRev (EtOH)

B : Alcohols, Phenols Class 12 Notes | EduRev Ester part is not affected by NaBH4

C : Alcohols, Phenols Class 12 Notes | EduRev Ester part and keto parts are affected by LiAlH4

D : Alcohols, Phenols Class 12 Notes | EduRev

E : Alcohols, Phenols Class 12 Notes | EduRev

 

(5) By reaction of nitrous acid on aliphatic primary amines.

General reaction: R-NH2 + HONO Alcohols, Phenols Class 12 Notes | EduRev R-OH +N2  + H2O

Mech.

R-NH2Alcohols, Phenols Class 12 Notes | EduRev (RAlcohols, Phenols Class 12 Notes | EduRev) Alcohols, Phenols Class 12 Notes | EduRev ROH +N2 +Alcohols, Phenols Class 12 Notes | EduRev

e.g. (i) C2H5NH2 +HNO2Alcohols, Phenols Class 12 Notes | EduRev C2H5OH+ N+ H2O

 

(ii) CH3-CH2-Alcohols, Phenols Class 12 Notes | EduRev +HONO Alcohols, Phenols Class 12 Notes | EduRev CH3-CH2-Alcohols, Phenols Class 12 Notes | EduRev+ N2 +H2O

Mech.

Alcohols, Phenols Class 12 Notes | EduRev


(6) Hydroxylation: Forms vicinal diols (glycols).

Converting an alkene to a glycol requires adding a hydroxy group to each end of the double bond. This addition is called hydroxylation of the double bond.

(a) Syn hydroxylation, using KMnO/ NaOH or using OsO4/H2O2

General reaction :

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


(b) Anti hydroxylation, using peracids.

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

Chemical reactions of alcohols: 

1. Reaction with hydrogen halides.

General reaction :

R - OH HX Alcohols, Phenols Class 12 Notes | EduRev R - X H2O (R may rearrange)

Reactivity of HX : Hl > HBr > HCl

Reactivity of ROH: allyl > benzyl > 3o > 2o > 1o

Mechanism R - OH Alcohols, Phenols Class 12 Notes | EduRev R-Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev R-X

 

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


2. Reaction with Phosphorus trihalides: 

(1) Several phosphorus halides are useful for converting alcohols to alkyl halides. PBr3, PCl3, & PCl5 work well and are commercially available.

(2) Phosphorus halides produce good yields of most primary and secondary alkyl halides, but none works well with ter. alcohols. The two phosphorus halides used most often are PBr3 and the P/ I2 combination.
General reaction :

3R - OH + PX3 Alcohols, Phenols Class 12 Notes | EduRev 3R - X + H3PO

Mechanism:

The mechanism for the reaction involves attachment of the alcohol group on the phosphorus atom, displacing a bromide ion and forming a protonated alkyl dibromophosphite (see the following reaction).

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

In a second step a bromide ion acts as a nucleophile to displace HOPBr2, a good leaving group due to the electronegative atoms bonded to the phosphorus.

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev RCH2X HOPX2

e.g. Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

3. Reaction with thionyl chloride

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev R-Cl SO2 HCl

 

4. Dehydration of alcohols

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev H2O (Rearrangement may occur)

Mechanism 

Step 1 :Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

Step 2 :Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Step 3 :Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Reactivity of ROH : 3º > 2º > 1º


5. Reaction with metals

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

e.g.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

6. Ester formation

General reaction: 

Alcohols, Phenols Class 12 Notes | EduRev  + Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev + H2O

e.g. CH3CH2O - H + Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev  + H2O

Alcohols, Phenols Class 12 Notes | EduRev  + Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

 

7. Oxidation reactions 

(a) oxidation of primary alcohols

Oxidation of primary alcohol initially forms an aldehyde. Obtaining the aldehyde is often difficult since most oxidizing agents are strong enough to oxidize the aldehydes formed. CrO3 acid generally oxidizes primary alcohol all the way upto the carboxylic acid


(b) oxidation of secondary alcohols-

Sec. alcohols are easily oxidized to give excellent yields of ketones. The chromic acid reagent is often best for laboratory oxidations of secondary alcohols. The active species in the mixture is probably chromic acid, H2CrO4, or the acid chromate ion, Alcohols, Phenols Class 12 Notes | EduRev


(c) Resistance of tertiary alcohols to oxidation-

Oxidation of ter-alcohol is not an important reaction in organic chemistry. Ter-alcohols have hydrogen atoms on the carbonyl carbon atom, so oxidation must take place by breaking C-C bonds. These oxidations require severe conditions and result in mixtures of products.

Primary

Alcohols, Phenols Class 12 Notes | EduRev

Secondary

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Tertiary

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevno reaction

e.g. 

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev

Ex.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevA

Identify A

Ans.Alcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRevAlcohols, Phenols Class 12 Notes | EduRev


Some Commercially Important Alcohols

Methanol and Ethanol

Methanol (CH3OH) and ethanol (C2H5OH) are the simplest members of the primary alcohol family and have a wide range of applications in the fuel industry. Some important uses of methanol and ethanol are listed in this article.

Uses of Ethanol

  • Owing to its antibacterial and antifungal properties, ethanol (also known as ethyl alcohol) is used in many hand sanitizers and medical wipes.
  • Ethanol is also used as an antiseptic and as a disinfectant.
  • In cases of ethylene glycol poisoning or methyl alcohol poisoning, ethanol is often administered as an antidote.

Alcohols, Phenols Class 12 Notes | EduRev

  • Several medications that are insoluble in water are often dissolved in ethanol. For example, ethanol (in concentrations ranging from 1% to 25%) is used as a solvent for some analgesics and mouthwashes.
  • Ethanol is the primary ingredient in many alcoholic drinks that are orally consumed for recreational purposes. It acts as a psychoactive drug by reducing anxiety and creating a feeling of euphoria in Humans. However, it also impairs cognitive and motor functions and acts as a central nervous system (CNS) depressant.
  • Ethanol is used industrially in the production of ethyl esters, acetic acid, diethyl ether, and ethyl amines.
  • This compound is widely used as a solvent due to its ability to dissolve both polar and nonpolar compounds.
  • Since it has a melting point of -114.1oC, ethanol is used as an ingredient in cooling baths in several laboratories. It also serves as the active fluid in many spirit thermometers.

Uses of Ethanol as a Fuel

  • Ethanol is widely used as a fuel additive and as an engine fuel. Some forms of gasoline are known to contain up to 25% ethanol. 
  • This compound has also been used as rocket fuel in some bipropellant rockets. When used in fuel, ethanol is believed to reduce carbon monoxide and nitrogen oxide emissions. 
  • Since it is widely available and has low toxicity and cost, ethanol is used in direct-ethanol fuel cells (or DEFCs). However, commercially used fuel cells generally use methanol, hydrogen, or natural gas.

Uses of Methanol

  • Methanol is widely used in the production of acetic acid and formaldehyde.
  • In order to discourage the recreational consumption of ethanol, methanol is often added to it as a denaturant.
  • This compound is also used as an antifreeze (an additive that is used to lower the freezing point of a liquid) in many pipelines.
  • It is also used in sewage treatment plants since it serves as a carbon-based food source for denitrifying bacteria.
  • The polyacrylamide gel electrophoresis (PAGE) technique involves the use of methanol as a destaining agent.
  • A mixture of water and methanol is used in high-performance engines in order to increase power.
  • Methanol is used in the production of hydrocarbons, olefins, and some aromatic compounds.
  • It is also used in the production of methyl esters and methylamines.
Alcohols, Phenols Class 12 Notes | EduRevUses of Methanol in Fuel
  • Methanol can be used as a fuel in several internal combustion engines. The chemical equation for the burning of methanol is given by:
  • 2CH3OH + 3O2 → 4H2O + 2CO2
  • However, the primary disadvantage of methanol as a fuel is that it has a tendency to corrode aluminum and some other metals. 
  • Another shortcoming of methanol as a fuel is that its energy density is approximately half of the energy density offered by gasoline.An advantage of methanol as a fuel is that it is relatively easy to store. 
  • The storage of liquid methanol is much easier than the storage of hydrogen gas or natural gas. Other merits of this compound include its biodegradability and its short half-life in groundwater.
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