Tag: hydroxy compounds and ethers

Questions Related to hydroxy compounds and ethers

Oxygen atom of ether is: 

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. very active

  2. replaceable

  3. active

  4. comparatively inert

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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.

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. High temperature

  2. High vaccum

  3. Cold

  4. None of the above

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Correct Option: A
Explanation:

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

Diethyl ether can be decomposed with:

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. $HI$

  2. $KMnO _4$

  3. $NaOH$

  4. $H _2O$

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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:

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. thioalcohol

  2. thioether

  3. thioester

  4. thioacetal

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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 :

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. $HCl < HBr < HF$

  2. $HI > HBr > HCl $

  3. $HF < HCl < HBr $

  4. none of these

Show answer
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: 

chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

  1. phenol and ethane

  2. bromobenzene and ethane

  3. phenol and ethyl bromide

  4. bromobenzene and ethanol

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Correct Option: A

Alcohols of low molecular weight are:

chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

  1. soluble in water

  2. soluble in water on heating

  3. insoluble in water

  4. insoluble in all solvents.

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Correct Option: A
Explanation:

Alcohols of low molecular weight are soluble in water while that of high molecular weight are insoluble in water .because of high hydrogen bonding in low molecular weight Alcinous.

Which of the following statements is not correctly showing the trend of the properties mentioned ?

chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

  1. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Solubility)}{CH _3CH _2CH _2CH _2OH}$

  2. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Boiling point)}{CH _3CH _2CH _2CH _2OH}$

  3. $CH _3CH _2CH _2OH > CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH >\underset{Boiling \, point}{CH _3-\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}C}}}-OH}$

  4. $CH _3-{\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}{C}}}}}-OH$<$CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH$ <$CH _3CH _2CH _CH _2OH$

Show answer
Correct Option: D
Explanation:
Boiling point and solubility of alcohols is determined by the ease and extent of H-bonding among the alcohol molecules. More is the hydrogen bonding higher is the boiling point and solubility in water. Thus, tertiary alcohols being highly hindered will have least hydrogen bonding and thus low boiling point/solubility as compared to less hindered secondary alcohol.
Therefore the order of boiling point is primary alcohol>secondary alcohol>tertiary alcohol as:
$CH _3CH _2CH _2OH>CH _3CH(CH _3)CH _2OH>CH _3C(CH _3) _2OH$
In case of linear versus branched alcohol, linear alcohol has higher melting/boiling points due to better stacking and surface area contact.
But in case of highly branched vs. branched molecules more sphere-like structure of the molecule better is the stacking thus higher will be the melting point. Thus order of melting point will be
$CH _3CH(CH _3)CH _2OH<CH _3C(CH _3) _2OH<CH _3CH _2CH _2CH _2OH$
A and B. Solubility and boiling point of alcohols depends on the chain length. Longer is the chain length, lesser is the solubility/boiling point as the extent of H-bonding decreases. Also, the hydrophobic nature of the hydrocarbon chain reduces the solubility.
thus order of solubility and boiling point will be:
$CH _3CH _2OH>CH _3CH _2CH _2OH>CH _3CH _2CH _2CH _2OH$

Which of the following is not a characteristic of alcohol ?

chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

  1. They are lighter than water.

  2. Their boiling points rise fairly uniformly with rising molecular weight.

  3. Lower members are insoluble in water and organic solvents but the solubility regularly increases with molecular mass.

  4. Lower members have a pleasant smell and burning taste, higher members are colourless and tasteless.

  5. Higher members have a pleasant smell and burning taste, lower members are colourless and tasteless.

Show answer
Correct Option: C
Explanation:
A. Alcohols are lighter than water because water molecules are closely packed together due to extensive H-bonding, which means that it has more mass in the same volume than either alcohol or oil. In addition, alcohol is made up of carbon and hydrogen atoms while water is made up of oxygen and hydrogen atoms.
B. Their boiling points rise fairly uniformly with rising molecular weight this is because boiling point depends on the intermolecular interactions such as H-bonding which decreases as the chain length decreases.
C. Lower members are soluble in water and organic solvents but the solubility regularly decreases with molecular mass because of ease of H-bonding in smaller alcohol molecules than those having long hydrocarbon chain.
D. Lower members have a pleasant smell and burning taste, higher members are colourless and tasteless.

Unlike phenol, 2,4-dinitrophenol is soluble in sodium carbonate solution in water because ?

chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

  1. presence of two - $NO _2$ groups in the ring makes 2 , 4 - dinitrophenol a stronger acid than phenol.

  2. presence of two - $NO _2$ groups in the ring makes 2 , 4 - dinitrophenol a weaker acid than phenol.

  3. presence of two $-NO _2$ groups make the hydrogen bonding easier, making 2 , 4-dinitrophenol soluble.

  4. nitro group reacts with $Na _2CO _3$ while -$OH$ group does not.

Show answer
Correct Option: A
Explanation:

Presence of two electron withdrawing $-No _2$ groups in the ring makes 2,4-dinitrophenol a stronger acid than phenol. Hence it react with aqueous  $Na _2CO _3$ solution to form sodium salt thus making it soluble in $Na _2CO _3$ .