Alcohols Phenols and Ethers Test

Result

Alcohols Phenols and Ethers Test - 48

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Weekly Quiz Competition

Question 1
1 / -0

Ethers can be prepared by?

A
dehydration of acids

B
hydrolysis of alkyl halides

C
dehydrogenation of alcohols

D
dehydration of alcohols

Solution

Ethers can be prepared by dehydration of alcohols.
Eg: Ethanol is dehydrated in presence of $$H_SO_4$$ at $$413K$$ to give ethoxyethane at $$413K$$ . It is a neucliophilic bimolecular reaction $$(S_n2)$$.
Question 2
1 / -0

The number of carbon atoms present in a molecule of simple ether is:

A
always even

B
always odd

C
either even or odd

D
unpredictable

Solution

Simple ethers have the same alkyl groups on both sides of the Oxygen atom.
Like, $$CH_3-O-CH_3$$
Thus, the number of carbon atoms is always even.
Hence, Option A is correct.
Question 3
1 / -0

The order of reactivity of the following alcohols towards dehydration is:

A
$$IV > I > II > III$$

B
$$III > IV > II > I$$

C
$$II > I > III > IV$$

D
$$II > III > I > IV$$

Solution

Reactivity of alcohol towards dehydration is increased by the stability of the carbocation formed subsequently. Order of carbocation stability is :
$$tertiary>secondary>primary.$$
Also presence of $$+I$$ groups like $$CH_3$$ increases the stability.
According to this the order of reactivity is ,
$$II>I>III>IV$$
Question 4
1 / -0

Mixed ether will not be formed in the reaction?

A
$$CH_3OCH_2Cl + C_2H_5MgBr$$

B
$$CH_2N_2 + C_2H_5OH$$

C
$$C_2H_5ONa + CH_3I$$

D
$$C_2H_5OH + H_2SO_4 (140^0C)$$

Solution

Option D is the correct answer.
$$C_2H_5-OH+H_2SO_4\ (140°C) \rightarrow C_2H_5-O-C_2H_5+H_2O$$
Ethyl alcohol when heated with Sulphuric acid at 140°C produces a symmetric ether i.e. Diethyl ether.
Question 5
1 / -0

The formation of oxanium salt of ether is due to:

A
protonation of O atom in ether

B
donation of an e pair by O atom in ether

C
the attachment of a proton to O atom in ether by co-ordination

D
all the above

Solution

Protonation of oxygen atom in ether as oxygen in ether act as nucleophile.
Question 6
1 / -0

Which of the following is most reactive towards the acid-catalysed dehyydration?

A

B

C

D

Solution

In acid catalysed reaction, the $$-OH$$ group is removed and carbocation formation takes place. More stable the carbocation, more will be the reactivity for this reaction. Carbocation is stabilized by conjugation with double bond, and its stability is also in the order.
$$tertiary>secondary>primary$$
According to this, option $$C$$ will be the most reactive.
Question 7
1 / -0

$$CH_{2} = CH_{2} + H_{2}SO_{4} \xrightarrow[]{75 - 80^{\circ}C} A \xrightarrow[warm]{H_{2}O} B$$
$$A$$ and $$B$$ in the above reaction are:

A
$$C_{2}H_{5}OH ; C_{2}H_{5}HSO_{4}$$

B
$$(C_{2}H_{5})_{2}SO_{4} ; C_{2}H_{5}OH$$

C
$$C_{2}H_{5}HSO_{4} ; C_{2}H_{5}OH$$

D
$$C_{2}H_{5}OH ; (C_{2}H_{5})_{2}SO_{4}$$

Solution
Question 8
1 / -0

By which of the following methods alcohol can be prepared in excellent yield ?

A
From alkenes

B
By hydroboration-oxidation

C
From carbonyl compounds

D
From Grignard reagent
Question 9
1 / -0

In an aqueous solution at $${25}^{o}C$$ has twice as many $${OH}^{-}$$ as pure water its $$pOH$$ will be:

A
$$6.699$$

B
$$7.307$$

C
$$7$$

D
$$6.98$$

Solution

Option $$A$$ is the correct answer.
We know that pure water at 25°C has $$10^{-7} M$$ of $$OH^-$$.
According to the problem, the aqueous solution at the same temperature has $$2 \times10^{-7}M$$ $$OH^-$$
Therefore, its $$pOH = -log(2 \times10^{-7})$$
$$pOH = 6.6989$$
$$ or, pOH = 6.699$$
Question 10
1 / -0

Which of the reagents on reaction with cyclohexanol gives best yield of cyclohexene?

A
Conc. $$H_{3}PO_{4}$$

B
Conc. $$HCl$$

C
Conc. $$HBr$$

D
Conc. $$HCl$$ with $$ZnCl_{2}$$

Solution