Alcohols Phenols and Ethers Test

Result

Alcohols Phenols and Ethers Test - 40

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Weekly Quiz Competition

Question 1
1 / -0

Which is the only alcohol that can be prepared by the indirect hydration of alkene?

A
Ethyl alcohol

B
Propyl alcohol

C
Isobutyl alcohol

D
Methyl alcohol

Solution

Alkene is treated with sulfuric acid to give alkyl sulphate esters. In the case of ethanol production, this step can be written:

$$H_2SO_4 + C_2H_4 \rightarrow C_2H_5-O-SO_3H$$

Subsequently, this sulphate ester is hydrolyzed to regenerate sulphuric acid and release ethanol:

$$C_2H_5-O-SO_3H + H_2O \rightarrow H_2SO_4 + C_2H_5OH$$

This two step route is called the "indirect process".
Only in case of ethane it will produce ethyl alcohol while in case of other alkenes product is according to $$Markovnikov's\ Rule$$.
Methyl alcohol can't be produced by indirect hydration of alkene.
Question 2
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Which of the following compounds decolourizes aqueous bromine and gives white fumes of $$HCl$$ on reaction with $$PCl_{5}$$?

A
$$CH_{3}COCH_{2}CH - CH_{2}$$

B
$$CH_{3}CH_{2}CH_{2}CH_{2}CH_{3}$$

C
$$CH_{3}CH = CHCH_{2}CH_{2}OH$$

D
$$CH_{3}OCH_{2}CH_{2}CH_{2}CH_{2}OH$$

Solution

$$CH_3-CH=CH-CH_2-CH_2-OH+PCl_5\longrightarrow K_3C-CH=CH-CH_2-CH_2-Cl+MCl+POCl_3$$
$$\downarrow$$ $$Br_2|H_2O$$
Colour decolorises due to the presence of double bond.
Question 3
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The IUPAC name for the compound given below is:

A
$$(2R, 3Z)$$ - 7 - phenylhept - 3- en - 2 - ol

B
$$(2S, 3Z)$$ - 7 - phenylhept - 3- en - 2 - ol

C
$$(2R, 3E)$$ - 7 - phenylhept - 3- en - 2 - ol

D
$$(2S, 3E)$$ - 7 - phenylhept - 3- en - 2 - ol
Question 4
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Among the following compounds, the one which can be dehydrated most easily is:

A
$$CH_{ 3 }-CH_{ 2 }-\overset { \overset { CH_{ 3 } }{ | } }{ \underset { \underset { OH }{ | } }{ C } }-CH_{ 2 }CH_{ 3 }$$

B
$$CH_3-CH_2-CH_2-\underset { \underset { OH }{ | } }{ C } H-CH_3$$

C
$$CH_3-CH_2-CH_2-CH_2-CH_2-OH$$

D
$$(CH_3)_2CH-CH_2-CH(OH)-CH_3$$

Solution

The compound which can be easily dehydrated will form most stable carbocation after removal of $$H_{ 2 }O$$ molecule.

Since stability of carbocation follows 3 degree> 2 degree> 1 degree,

so, compound $$A$$ is most easily dehydrated.

Option A is correct.
Question 5
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Which of the following statements is incorrect regarding preparation of alcohols?

A
Aldehydes and Ketones on catalytic reduction by [H] give primary alcohol and secondary alcohol respectively

B
Ketones on reaction with Grignard’s reagent gives tertiary alcohol

C
Aldehydes on reaction with Grignard’s reagent gives primary or secondary alcohol

D
Alkyl halides on reaction alcoholic potash gives alcohol

Solution
Question 6
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Which of the following phenols has lowest solubility in water?

A
Phenol

B
o-Nitrophenol

C
m-Nitrophenol

D
p-Nitrophenol

Solution

$$O-$$ nitrophenol undergoes creation because of intra-moleculer hydrogen bonding. So, it is least soluble.
Question 7
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An Alcohol X pass over Cu at 300C, then produced compound decolourised Bromine liquid, X is:

A

B

C

D

Solution

Since the compound formed finally decolourises Bromine water, so it must be alkene. Now $$3$$ degree alcohol were dehydrated with heated Cu forms alkene. So, $$X$$ is a $$3$$ degree alcohol.
Question 8
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(A) $$CH_3-\underset{\underset{\,\,\,\,CH_3}{|}}CH-CH_2-CH_2-OH$$
(B) $$CH_3-\overset { \underset { | }{ \, \, \, \, \, OH } }{ \underset { \overset { | }{ \, \, \, \, \, CH_{ 3 } } }{ C } }-CH_2-CH_3 $$
(C) $$CH_3\overset{\overset{CH_3}{|\,\,\,\,\,}}{CH}-\overset{\overset{OH}{|\,\,\,}}{CH}-CH_3$$
The order of given alkanols $$A,B,C$$ in their reactivity towards acid catalysed dehydration is:

A
$$A> B> C$$

B
$$B> A> C$$

C
$$B> C> A$$

D
$$C> B> A$$

Solution

Carbocation formed during reaction are referred to the image above:
Therefore stability of carbocations have the order $$3 degree> 2degree> 1 degree$$ and $$CH_{ 3 }$$ is $$+$$ group so, the order of stability is $$: B>C>A$$
(B) $$CH_3-\overset { \underset { | }{ \, \, \, \, OH } }{ \underset { \overset { | }{ \, \, \, \, CH_{ 3 } } }{ C } }-CH_2-CH_3 \rightarrow CH_3-\overset { \underset { | }{ \, \oplus} }{ \underset { \overset { | }{ \, \, \, \, \, CH_{ 3 } } }{ C } }-CH_2-CH_3 $$ $$ (2^o)$$
(C) $$CH_3-\overset{\overset{\,\,\,CH_3}{|}}{C}H-\overset{\overset{OH}{|}}{C}H-CH_3 \rightarrow CH_3-\underset{\underset{\,\,CH_3}{|}}{C}-\underset{\oplus}{Ch}-CH_3\underset{(2^o)}{CH_3}$$
Question 9
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Dehydration of the following in increasing order is:

A
$$I < II < III < IV$$

B
$$II < III < IV < I$$

C
$$I < III < II < IV$$

D
$$I < IV < II < III$$

Solution

Phenol $$(I)$$ is stable aromatic compound. So it is most stable. The diene $$(IV)$$ undergoes quick dehydration because it will form stable phenol. The alkene $$(III)$$ undergoes dehydration. less readily because it gives a more stable diene. Alcohol $$(II)$$ undergoes much lesser dehydration to form alkene. . So, order is: $$4> 3> 2> 1.$$
Question 10
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Diols (I - IV) which react with $$CrO_{3}$$ in aqueous $$H_{2}SO_{4}$$ and yield products that readily undergo decarboxylation on heating are:

A
I and II

B
II and III

C
II and IV

D
I and IV

Solution