Alcohols Test

Result

Alcohols Test - 7

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Weekly Quiz Competition

Question 1
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Which of the following tests can be used to distinguish between two isomeric ketones: 3- pentanone and 2- pentanone?

A
I₂ /NaOH

B
NaSO₃ H

C
NaCN/HCl

D
2,4-DNP

Solution

2- pentanone is a methyl ketone. It undergoes haloform reaction with iodine in presence of sodium hydroxide, to form yellow precipitate of iodoform. 3- pentanone is not a methyl ketone. It does not undergo haloform reaction. Hence, 3- pentanone and 2- pentanone can be distinguished by reaction with iodine in presence of NaOH.
Question 2
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An organic compound X (C₅ H₁₂ O) gives effervescence with NaH. X on treatment with acidic CrO₃ solution turns solution to blue-green forming C₅ H₁₀ O₂ . Also X can be resolved into enantiomers. The correct statement regarding X is

A
It is 2-pentanol

B
It is 3-pentanol

C
With HBr, it gives achiral alkyl bromide

D
The oxidation product C₅ H₁₀ O₂ is achiral

Solution

X is a primary, chiral alcohol.
Question 3
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An organic compound C₄ H₁₀ O (X) on reaction with I₂ /red-P give s C₄ H₉ I which on further reaction with AgNO₂ gives C₄ H₉ NO₂ (Y). Y on treatment with HNO₂ forms a blue solution which turns to red on making solution slightly alkaline. The possible identity of X is

A
1-butanol

B
2-methyl-1-pentanol

C
2-butanol

D
Either (a) or (b)

Solution

X must be a primary alcohol as indicated by Victor Meyer 's test. Both (a) and (b) are primary satisfy the condition.
Question 4
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An organic compound X (C₇ H₁₆ O) on treatm ent with concentrated HCI solution forms immediate turbidity even in the absence of ZnCl₂ . Also, X is resolvable into enantiomers. The correct statement concerning X is

A
It is 3-methy!-2-hexanol

B
It turns orange CrO₃ /H₂ SO₄ solution green

C
It is 3-methyl-3-hexanol

D
It forms yellow precipitate with I₂ /NaOH

Solution
Question 5
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Which reagent given below does not produce any visible change when added to ethylene glycol?

A
NaNH₂

B
CrO₃ /H₂ SO₄

C
H₂ CO/H₂ SO₄

D
NaH

Solution

H₂ CO forms cyclic acetal with ethylene glycol but the change cannot be observed visually, in all other cases, change can be observed visually-effervescence with NaNH₂ and NaH while colour change with CrO₃ -H₂ SO₄ .
Question 6
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Which of the following is least likely to form turbidity with HCI in the presence of ZnCI₂ at room temperature?

A

B

C

D

Solution

Although it is secondary alcohol, it forms a very unstable carbocation (Cl is electron withdrawing group), hence it does not give turbidity with Lucas reagent in cold condition.
Question 7
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The correct statement regarding 3-ethyl-3-hexanol is

A
It changes colour of CrO₃ /H₂ SO₄

B
It is oxidised on heating with copper metal, producing ketone

C
It gives yellow precipitate with NaOH/I₂

D
It changes colour of cerric nitrate [Ce(NO₃ )₄ ] from yellow to r

Solution

All alcohols react (1 °, 2 °and 3 °) with cerric nitrate and a colour change from yellow to red is observed.
Question 8
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An alcohol has molecular formula C₆ H₁₂ O X and it gives immediate turbidity with cold, concentrated HCI even in the absence of ZnCI₂ . X can also be obtained by treatment of an ether with excess of CH₃ MgBr followed by acid hydrolysis. Hence, the correct statement regarding X is

A
It is 3-methyl-3-pentanol

B
It is 2-methyl-3-pentanol

C
It is 2-methyl-2-pentanol

D
Either (b) or (c)

Solution
Question 9
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One or More than One Options Correct Type

Direction : This section contains 4 multiple choice questions. Each question has four choices (a), (b), (c) and (d), out of which ONE or MORE THAN ONE are correct.

Q.

Which reagent(s) can be used to differentiate between 2-pentanol and 1-pentanol?

A

B
HCI/ZnCI2

C
CrO₃ -H₂ SO₄

D
Option A,B are Correct

Solution

2-pentanol forms yellow precipitate of CHI₃ with I₂ /NaOH but 1-pentanol does not. 2-pentanol give immediate turbidity with Lucas reagent but 1 -pentanoi does not gives turbidity with Lucas reagent at room temperature. Both alcohols (1 °and 2 °) change colour of chromic acid solution from orange to blue green and both give effervescence of NH₃ (g) with NaNH₂ , hence these reagents cannot be used for distinction between 1 °and 2 °alcohols.
Question 10
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Alcohols given below that behaves like 1 °-aliphatic alcohol in Lucas test is/are

A

B

C

D
Option A,C are Correct

Solution

Both have electron withdrawing groups, destabilises carbocation, do not form turbidity with Lucas reagent at room temperature like primary alcohols. Option (b) and option (d) have electron donating groups, stabilises benzylic carbocation, forms immediate turbidity with Lucas reagent like 2 °and 3 °alcohols.