Distinguish between primary, secondary and tertiary alcohols

Distinguish between primary, secondary and tertiary alcohols

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Definitions are assigned to carbon atoms based on the number of other carbon atoms they are connected to

• Primary carbons : Carbons connected to one carbon only.

• Secondary carbons : Carbons connected to two carbon atoms.

• Tertiary carbons : Carbons connected to three carbon atoms.

• And if four carbons are connected to a carbon, then it is a quaternary carbon.

Summary

Multiple Choice

the number of primary carbons in neopentane is

• 0

• 1

• 4

Multiple Choice

the number of tertiary carbons in neopentane is

• 0

• 1

• 4

Multiple Choice

How many secondary carbons are there in the given structure?

• 3

• 2

• 5

• 0

Multiple Choice

Which of the following substances has only secondary carbon atoms in its structure?

• methane

• Ethyne

• Ethane

• Propane

• Cyclohexane

Multiple Choice

The number of primary, secondary and tertiary carbons in 3,4-dimethylheptane are respectively

• 4,3 and 2

• 2, 3 and 4

• 4, 2 and 3

• 3, 4 and 2

Amines are a bit different

Amides are similar to Amines

Multiple Choice

This compound is classified as a

• primary amine

• secondary amine

• tertiary amine

• primary amide

• secondary amide

Multiple Choice

Which compound is a tertiary amine?

Multiple Choice

The given structure is a

• primary amino acid

• primary amide

• secondary amino acid

• secondary amide

Multiple Choice

Which pairing of alcohol and class is incorrect?

• Butan-2-ol; secondary alcohol.

• 2-Methylpropan-2-ol; tertiary alcohol.

• Propan-1-ol; primary alcohol.

• Pentan-3-ol; tertiary alcohol.

Test for type of alcohol: Method 1​

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Oxidation

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Methods to distinguish between primary, secondary and Tertiary alcohols​

Oxidation of alcohols depend on their type (primary, secondary or tertiary)

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and the oxidizing agent (strong or weak)​

Tertiary alcohols are not oxidised

The structural requirements for the oxidation to carbonyl products should now be obvious

• The carbon atom bonded to oxygen must also bear a hydrogen atom. 

• Tertiary alcohols (R₃C–OH) cannot be oxidized in this fashion.

• Ethers (R–O–R) cannot be oxidized in this fashion as the oxygen atom must be bonded to a hydrogen atom

No matter how powerful, or magical, none of them are able to oxidize tertiary alcohol.

Chromic Acid Test (Jones test)

A solution of CrO₃ in H₂SO₄ is a test for polar functional groups that can be oxidized, which includes aldehydes, primary alcohols, and secondary alcohols.

• Tertiary alcohols give a negative result with this test

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Negative (a) and positive (b) results for the chromic acid test.

Chromic Acid Test (Jones test)

..continued..

The orange Cr⁶⁺ reagent converts to a blue-green Cr³⁺ species, which often precipitates in acetone.

Chromic Acid Test (Jones test)

..continued..

Chromic acid results (left to right): 

t-butanol (tertiary, negative),

1-propanol (primary, positive),

2-propanol (secondary, positive),

benzaldehyde (positive),

Multiple Choice

CH₃CH₂OH can be converted into CH₃CHO by

• catalytic hydrogenation

• treatment with LiAlH₄

• treatment with pyridinium chlorochromate

• treatment with KMnO₄

Multiple Choice

Which of the following reagents gives this reaction

• KMnO₄

Multiple Select

Select the reagents that can be used to carry out this transformation

• KMnO₄

Multiple Select

Which of the following pairs of compounds can be distinguished by Jones oxidation?

• 1-propanol and 2-propanol

• t-butyl alcohol and sec-butyl alcohol

• 1-butanol and butanal

• cyclohexanol and benzaldehyde

Test for type of alcohol: Method 2

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​Dehydrogenation

Methods to distinguish between primary, secondary and Tertiary alcohols​

Dehydrogenation of alcohol

• Vapors of an alcohol are passed over copper catalyst heated at 573K

• The product formed depends on the alcohol

Dehydrogenation of alcohol

Dehydrogenation of alcohol ..continued

• When the vapors of a primary alcohol are passed over copper heated at 573K, the corresponding aldehyde is formed.

Dehydrogenation of alcohol ..continued

• When the vapors of a secondary alcohol are passed over copper heated at 573K, the corresponding ketone is formed.

Dehydrogenation of alcohol ..continued

• Tertiary alcohol when reacted with copper catalyst at 573K are not dehydrogenated but undergoes dehydration to give the corresponding alkene.

• Dehydration follows Seytzeff rule.

The dehydration of alcohols is not used in the laboratory setting

because many compounds do not survive

the reaction temperature of 300°C

Multiple Choice

What happens when tertiary butyl alcohol is passed over heated copper at 300°C?

• Secondary butyl alcohol is formed

• 2-methylpropene is formed

• 1-butene is formed

• Butanol is formed

Multiple Choice

When vapors of the given compound is treated with Copper at 300°C, the product is more likely to be

Multiple Choice

1-propanol and 2-propanol can be best distinguished by

• Oxidation with KMnO₄ followed by reaction with Fehling solution.

• Oxidation with acidic dichromate followed by reaction with Fehling solution.

• Oxidation by heating with copper followed by reaction with Fehling solution.

• Oxidation with concentrated H2SO4 followed by reaction with Fehling solution

Test for type of alcohol: Method 3

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Luca's test

Methods to distinguish between primary, secondary and Tertiary alcohols​

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Luca's test

• The Lucas reagent is concentrated HCl

  and ZnCl₂.

• Alcohols can react through an S_N1 mechanism to produce alkyl halides that are insoluble in the aqueous solution and appear as a white precipitate or cloudiness.

• The test cannot be used for water-insoluble alcohols (generally > 5 carbon atoms), as they may produce a cloudiness or second layer whether reaction occurred or not.

Luca's test ..continued

• As the mechanism is S_N1, a tertiary alcohol reacts immediately

• A secondary alcohol reacts more slowly (perhaps in 5 minutes if at all)

• primary alcohols don't react at all.

• Benzylic alcohols (Ph−C−OH)

  (Ph−C−OH), allylic alcohols (C=C−C−OH)

  (C=C−C−OH) and propargylic alcohols (C≡C−C−OH)

  (C≡C−C−OH) give immediate results just like tertiary alcohols.

Multiple Choice

What is the correct order of reactivity of alcohols in the reaction with Luca's reagent?

• 1° > 2° > 3°

• 1° < 2° > 3°

• 3° > 2° > 1°

• 3° > 1° > 2° 

Multiple Choice

The compound which gives turbidity immediately with Lucas reagent at room temperature is

• 2-methyl propan-1-ol

• butan-1-ol

• butan-2-ol

• 2-methyl propan-2-ol

Multiple Select

Which of the following compounds will answer positively to Luca's test?

Test for type of alcohol: Method 4

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Victor Meyer's test

Methods to distinguish between primary, secondary and Tertiary alcohols​

Victor Meyer's test

•  In this methods 1°, 2° and 3° alcohols are subjected to a series of chemical analysis and the color of resulting solution is observed.

• 1° alcohol --> Red color

• 2° alcohol --> Blue color

• 3° alcohol --> No color

General series of reactions in Victor Meyer's test

Is the Victor Meyer test given by phenol? - NO

The first step of the test involves the reaction of the given sample with P+I₂ to convert R-OH to R-I

But phenol does not undergo nucleophilic substitution reaction in the given test conditions.

Multiple Select

Which of the following pairs of compounds can be distinguished by Victor-Meyer test?

• 1-propanol and 2-propanol

• t-butyl alcohol and sec-butyl alcohol

• 1-butanol and 1-propanol

• cyclohexanol and cyclopentanol

Multiple Select

In Victor-Meyer test, red color is shown by

• 1-propanol

• t-butyl alcohol

• 1-butanol

• cyclohexanol

Multiple Choice

In Victor Mayer's Test, which compound do we get at the end when tested with primary alcohol?

• Nitrolic acid

• Nitroalkane

• Pseudonitrol

• Glycerol

Multiple Choice

What colour is expected from neopentyl alcohol in Victor Meyer’s test?

• Orange

• Blue

• Red

• No colour