Tag: hydroxy compounds and ethers

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Questions Related to hydroxy compounds and ethers

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

Oxygen atom of ether is: 

  1. very active

  2. replaceable

  3. active

  4. comparatively inert
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

Diethyl ether can be decomposed with:

  1. $HI$
  2. $KMnO _4$
  3. $NaOH$
  4. $H _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

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
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $HI>HBr>HCl$

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

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
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethyl phenyl ether, an alkyl aryl ether, undergoes cleavage upon heating with concentrated HBr to yield phenol and an alkyl halide. Because the oxygen-phenyl bond has partial double bond character due to resonance, cleavage occurs at the alkyl-oxygen bond, producing phenol and ethyl bromide.

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

Alcohols of low molecular weight are:

  1. soluble in water

  2. soluble in water on heating

  3. insoluble in water

  4. insoluble in all solvents.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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. $CH _3-{\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}{C}}}}}-OH$<$CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH$ <$CH _3CH _2CH _CH _2OH$
Reveal answer Fill a bubble to check yourself
D Correct answer
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:
$CH _3CH _2OH>CH _3CH _2CH _2OH>CH _3CH _2CH _2CH _2OH$

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

Which of the following is not a characteristic of alcohol ?

  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.
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice chemistry hydroxy compounds and ethers physical properties of phenol physical properties of alcohols and phenols organic compounds with functional group containing oxygen (part-1)

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

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $Na _2CO _3$ .