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Chemical properties of ethers - class-XII

Description: chemical properties of ethers
Number of Questions: 17
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Tags: hydroxy compounds and ethers chemistry organic compounds containing c, h and o alcohols, phenols and ethers
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An ether is more volatile than alcohol having the same molecular formula. This is due to:

  1. intermolecular hydrogen bonding in ethers

  2. dipolar character of ethers

  3. alcohols having resonance structures

  4. intermolecular hydrogen bonding in alcohols


Correct Option: D
Explanation:

An ether which is almost nonpolar is more volatile than alcohol having same molecular formula .this is due to intermolecular hydrogen bonding in alcohols .so alcohols have high bonding point.

An organic compound with molecular formula $C _4H _{10}O$ does not react with sodium . With excess of HI it gives only one type of alkyl halide. The compound is:

  1. $C _2H _5OC _2H _5$

  2. $CH _3{\underset{OCH _3}{\underset{|}{C}}}HCH _3$

  3. $CH _3CH _2CH _2OCH _3$

  4. $CH _3CH _2CH _2CH _2OH$


Correct Option: A
Explanation:

$C _4H _{10}O$ can have two structures :


$CH _3CH _2CH _2CH _2OH$   and  $C _2H _5OC _2H _5$.

Since it does not react with Na metal, it can not be an alcohol.

$C _2H _5OC _2H _5 + \underset{excess}HI\rightarrow 2C _2H _5I + H _2O$

Which of the following products are not correctly matched in the given reactions?

  1. $C _2H _5OCH _3 + HBr \xrightarrow{373K} C _2H _5OH + CH _3Br$

  2. $C _2H _5OC _2H _5 + 2HI \rightarrow C _2H5I + C _2H _5OH$

  3. $C _2H _5OC _2H _5 + \overset{Excess}{HCl} \xrightarrow{Cold} [(C _2H _5) _2O^+H]Cl^-$

  4. $(CH _3) _3COC _2H _5 \xrightarrow{HI} (CH _3) _3CI + C _2H _5OH$


Correct Option: B
Explanation:

$C _2H _5-O-C _2H _5 +\underset{(excess)} 2HI \rightarrow 2C _2H _5I + H _2O$

Anisole on reaction with chloromethane in presence of anhydrous $AlCl 3$ gives __________.

  1. o-methyl anisole and p-methoxy anisole

  2. p-methyl anisole and p-methoxy anisole

  3. o-methyl anisole and p-methyl anisole

  4. o-methoxy acetphenone and p-methoxy acetophenone .


Correct Option: C
Explanation:
Anisole i.e. Phenyl methyl ether $CH _3OC _6H _5$ reaction with Chloromethane in the presence of anhy $AlCl _3$ electrophilic substitution reaction at ortho and para position w.r.t. methoxy group on benzene ring. It is called Friedel-craft alkylation reaction and represented as:
$C _6H _5OCH _3+ CH _3Cl \overset {AlCl _3}{\rightarrow} o-CH _3C _6H _5OCH _3+p-CH _3C _6H _5OCH _3$
Hence Anisole on reaction with chloromethane in presence of anhydrous AlCl3 gives o-methyl anisole and p-methyl anisole

The number of monochloro derivaties of 2-methoxy propane are possible are: 

  1. 2

  2. 1

  3. 3

  4. 4


Correct Option: C
Explanation:

$\quad \quad \quad OC{ H } _{ 3 }\ \hspace{2mm} \quad \quad \quad |\ { H } _{ 3 }C-CH-C{ H } _{ 3 }$

2-methoxypropane
The number of monochloro derivatives are 3. They are:
1) $\quad \quad \hspace{2mm} \quad OC{ H } _{ 3 }\ \quad \quad \quad \quad |\ { H } _{ 2 }C-CH-C{ H } _{ 3 }\ \quad |\ \hspace{2mm} Cl$
2) $\quad \quad  \quad OC{ H } _{ 3 }\ \quad \hspace{2mm} \quad \quad |\ { H } _{ 3 }C-C-C{ H } _{ 3 }\ \quad \quad \hspace{2mm} \quad |\ \quad \quad \quad Cl$
3) $\quad \quad  \quad OC{ H } _{ 2 }-Cl\ \quad \hspace{2mm} \quad \quad |\ { H } _{ 3 }C-C-C{ H } _{ 3 } $

Ether on carbonylation gives:

  1. Alkanoic acid

  2. Alkanone

  3. Alkyl alkonate

  4. Alkanal


Correct Option: C
Explanation:

The general reaction between Ether and Carbon monoxide is 


$R-O-R+CO \rightarrow R-CO-O-R$ 

Thus, it forms the ester Alkyl alkanoate.


Option C is the correct answer.

Ethers are considered as ____.

  1. mono alkyl derivatives of water

  2. alkoxy derivations of alkanes

  3. alkyl derivatives of fatty acids.

  4. condensation product of acid and alcohol.


Correct Option: D

The compound obtained by the reaction of diethyl ether with chlorine in the presence of sun light , is 

  1. Perchloro diethyl ether $H _5C _2-OC _2Cl _5$

  2. Perchloro diethyl ether $Cl _5C _2-O-C _2Cl _5$

  3. $\beta ,\beta '$ Dichloro diethyl ether $ClCH _2CH _2-O-CH _2CH _2Cl$

  4. $\alpha ,\alpha $ Dichloro diethyl ether


Correct Option: B

Diethyl ether reacts with $\displaystyle PCl _{5}$ to form:

  1. ethyl chloride

  2. phosphorous oxy trichloride

  3. 1,2-dichloroethane

  4. ethene


Correct Option: A,B
Explanation:

Diethyl ether reacts with Phosphorous pentachloride on heating to form ethyl chloride.

$C _2H _5-O-C _2H _5+PCl _5\longrightarrow 2C _2H _5Cl+POCl _3$

Isopropyle methyl ether when treated with cold hydrogen iodide gives

  1. isopropyl iodide and methyl iodide

  2. isopropyl alcohol and methyl iodide

  3. isopropyl alcohol and methyl alcohol

  4. isopropyl iodide and methyl alcohol


Correct Option: B

Oxygen atom of ether is: 

  1. very active

  2. replaceable

  3. active

  4. comparatively inert


Correct Option: D
Explanation:
Oxygen atom of ether is comparatively inert.

 $C-O-C$ linkage is quite stable. Under ordinary conditions, ethers are not acted upon by dilute acids, bases and most of the oxidizing and reducing agents. 

Hence correct answer is option D.

$C _2H _5-O-C _2H _5 +  HI \xrightarrow {?}  C _2H _5-OH + C _2H _5-I$
Identify the reaction condition, in which reaction occur.

  1. High temperature

  2. High vaccum

  3. Cold

  4. None of the above


Correct Option: A
Explanation:

The cleavage of ethers takes places with concentration $HI$ or $HBr$ at high temperature.

Diethyl ether can be decomposed with:

  1. $HI$

  2. $KMnO _4$

  3. $NaOH$

  4. $H _2O$


Correct Option: A
Explanation:

On heating with concentrated Hydrogen iodide $(HI)$ the C-O bond in ethers breaks forming alcohol and alkyl iodide. For example,

 ${ C } _{ 2 }{ H } _{ 5 }-O-{ C } _{ 2 }{ H } _{ 5 }+HI\longrightarrow { C } _{ 2 }{ H } _{ 5 }-I+{ C } _{ 2 }{ H } _{ 5 }OH$

 On boiling with excess of concentrated Hydrogen iodide $(HI)$, Alkyl iodide is formed.

${ C } _{ 2 }{ H } _{ 5 }-O-{ C } _{ 2 }{ H } _{ 5 }+2HI\longrightarrow 2{ C } _{ 2 }{ H } _{ 5 }-I+{ H } _{ 2 }O$

When an ether is treated with $P _2S _5$, it gives:

  1. thioalcohol

  2. thioether

  3. thioester

  4. thioacetal


Correct Option: B
Explanation:

When an ether is treated with $P _2S _5$, it gives thioether.


$5C _2H _5-O-C _2H _5+P _2S _5\rightarrow\underset{Thioether}{5C _2H _5-S-C _2H _5}$

Hence option B isthe correct answer.

Ethers are heated with excess of conc. hydrogen halide to give alkyl halide, then the reactivity order of hydrogen halide is :

  1. $HCl < HBr < HF$

  2. $HI > HBr > HCl $

  3. $HF < HCl < HBr $

  4. none of these


Correct Option: B
Explanation:

When $HX$ is in excess and reaction is carried out at high temperature. Iodine is a good nucleophile, displaces an alcohol molecule by $SN^2$ mechanism thus $HI>HBr>HCl$

Ethyl phenyl ether on boiling with conc. HBr gives: 

  1. phenol and ethane

  2. bromobenzene and ethane

  3. phenol and ethyl bromide

  4. bromobenzene and ethanol


Correct Option: A
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