An unknown alcohol is treated with the "Lucas reagent "to determine whether the alcohol is primary ,secondary or tertiary, Which alcohol reacts fastest and by what mechanism:

tertiary alcohol by S_N2

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secondary alcohol by S_N1

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tertiary alcohol by S_N1

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secondary alcohol by S_N2

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From amongst the following alcohols, the one that would react fastest with conc. HCl and anhydrous ZnCl₂, is

1-Butanol

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2-Butanol

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2-Methylpropan-2-ol

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2-Methylpropanol

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An ether is more volatile than an alcohol having the same molecular formula. This is due to

dipolar character of ethers

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alcohols having resonance structures

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inter-molecular hydrogen bonding in ethers

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inter-molecular hydrogen bonding in alcohols.

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When glycerol is treated with excess of HI, it produces:

Glycerol Triiodide

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2-iodopropane

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Allyl iodide

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Propene

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$\mathrm{H}_2 \mathrm{COH} . \mathrm{CH}_2 \mathrm{OH}$ on heating with periodic acid gives:

2 HCOOH

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$CHO$

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$2 \mathrm{CO}_2$

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For which of the following parameters the structural isomers $C_2H_5OH$ and $CH_3OCH_3$ would be expected to have the same values? (Assume ideal behaviour)

Heat of vaporisation

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Vapour pressure at the same temperature

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Boiling points

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Gaseous densities at the same temperature and pressure.

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The conjugate base of hydrazoic acid is

$N^{-3}$

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$N_{3}^{-}$

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$N_{2}^{-}$

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$HN_{3}^{-}$

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Concepts Covered - 5

Properties of Alcohols

Lower members of alcohols are colourless liquids whereas higher members are colourless solids.
Alcohols have higher boiling points.
Boiling point of alcohols increase with increase in member of OH group.
Lower members are highly soluble in water.

Acylation and Oxidation of Alcohols

Acylation of alcohols
Ethanoyl chloride reacts instantly with cold ethanol. There is a very exothermic reaction in which a steamy acidic gas is given off (hydrogen chloride) and ethyl ethanoate (an ester) is formed.

For example,

Oxidation of Alcohols
The nature of the oxidation products depends on whether the alcohol is primary, secondary or tertiary. The oxidising agents usually employed are acidified potassium dichromate, acidified or alkaline potassium permanganate or dilute nitric acid. It is a test of different alcohols as primary, secondary and tertiary alcohols give different products during oxidation.

Primary alcohols give acids having same number of carbon atoms with acidic KMnO₄ or K₂Cr₂O₇. For example,
Secondary alcohol on oxidation gives ketone which undergo further oxidation under drastic conditions by strong oxidizing agents like HNO₃to give acid with one carbon atom less than the alcohol. For example,
Tertiary alcohol cannot undergo oxidation by mild oxidizing agent as above however it can be oxidized under drastic conditions by strong oxidizing agents and the final product acid will have two carbon atom less than alcohol.

Haloform Reaction

Ethyl alcohol when heated with iodine and sodium hydroxide or aqueous sodium carbonate forms a yellow crystalline solid, iodoform. The reaction occurs as follows:

$\mathrm{C_{2}H_{5}OH\: +\: 4I_{2}\: +\: 6NaOH\: \overset{Heat}{\longrightarrow}\: CHI_{3}\: +\: 5NaI\: +\: HCOONa\:+\: 5H_{2}O}$

Methyl alcohol does not respond to the iodoform test. In place of iodine, bromine or chlorine can be taken when the corresponding compounds bromoform or chloroform are to be formed. The reaction in general is known as haloform reaction.

Pinacol Pinacolone Rearrangement

The pinacol rearrangement is the acid-catalyzed dehydration of glycols, which converts the glycol into an aldehyde or a ketone. When pinacols are treated with mineral acids, acid chlorides, ZnCl₂, or other electrophilic reagent, they rearrange to form ketones called pinacolones with the elimination of H₂O.

Mechanism

For example

NOTE: With unsymmetrical glycols, the product obtained is determined mainly by the OH that is lost as H₂O to give more stable carbocation and thereafter by the better migrating group.

Oxidative Cleavage with HIO4

At least 2-OH or 2 >C=O or 1-OH and 1 >C=O should be at adjacent carbons. HIO₄ works as an oxidising agent here.

Some examples include,