MCQ Questions for Class 12 Engineering Chemistry Alcohols,Phenols And Ethers Quiz 7

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

0%
always even
0%
always odd
0%
either even or odd
0%
unpredictable

Explanation

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.

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

Explanation

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.

Ethers can be prepared by?

0%
dehydration of acids
0%
hydrolysis of alkyl halides
0%
dehydrogenation of alcohols
0%
dehydration of alcohols

Explanation

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

$(S_n2)$ .

1049816_1109828_ans_b9f92433289b4025828e2f0190a8cb97.png

The formation of oxanium salt of ether is due to:

0%
protonation of O atom in ether
0%
donation of an e pair by O atom in ether
0%
the attachment of a proton to O atom in ether by co-ordination
0%
all the above

$CH_{2} = CH_{2} + H_{2}SO_{4} \xrightarrow[]{75 - 80^{\circ}C} A \xrightarrow[warm]{H_{2}O} B$

$A$ and

$B$ in the above reaction are:

0%
$C_{2}H_{5}OH ; C_{2}H_{5}HSO_{4}$
0%
$(C_{2}H_{5})_{2}SO_{4} ; C_{2}H_{5}OH$
0%
$C_{2}H_{5}HSO_{4} ; C_{2}H_{5}OH$
0%
$C_{2}H_{5}OH ; (C_{2}H_{5})_{2}SO_{4}$

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

0%
$IV > I > II > III$
0%
$III > IV > II > I$
0%
$II > I > III > IV$
0%
$II > III > I > IV$

Explanation

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 ,

$II>I>III>IV$

Which of the following is alcohol is least towards the acid-catalysed dehyydration?

Explanation

Acid catalyzed dehydration results into carbocation formation. Carbocation stability influences the reactivity for this reaction. The carbocation stability order is :

$\text{(Conjugation with double bond)>Tertiary>secondary>primary}$

Here option

$B$ will be least reactive.

In an aqueous solution at

${25}^{o}C$ has twice as many

${OH}^{-}$ as pure water its

$pOH$ will be:

0%
$6.699$
0%
$7.307$
0%
$7$
0%
$6.98$

Explanation

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

$pOH = -log(2 \times10^{-7})$

$pOH = 6.6989$

$or, pOH = 6.699$

$C-O-C$ bond in ethers can be cleaved by:

0%
${ H }_{ 2 }{ SO }_{ 4 }$
0%
${ LiAIH }_{ 4 }$
0%
$KOH$
0%
$HI$

Explanation

$C-O-C$ bond in ethers can be cleaved by

$H_2SO_4$ or conc.

$HI$ or

$LiAlH_4$

Mixed ether will not be formed in the reaction?

0%
$CH_3OCH_2Cl + C_2H_5MgBr$
0%
$CH_2N_2 + C_2H_5OH$
0%
$C_2H_5ONa + CH_3I$
0%
$C_2H_5OH + H_2SO_4 (140^0C)$

Explanation

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.

Alcohol can be dehydrated by:

0%
$(C{ H }_{ 3 }CO{ ) }_{ 2 }O$
0%
$(C{ H }_{ 3 }{ ) }_{ 2 }S{ O }_{ 4 }$
0%
HI/P
0%
Anhy $ZnC{ l }_{ 2 }/\Delta$

Explanation

Option D is the correct answer.

$R-CH_2-OH \xrightarrow{Anhy\ ZnCl_2/\Delta} R=CH_2$

In the reaction

$ROH+PBr_{3} \rightarrow RBr$
The number of moles of alcohol that may be converted into alkyl bromide by one mole of

$PBr_{3}$ is:

0%
$1$ mole
0%
$2$ mole
0%
$3$ mole
0%
none of the above

Explanation

From the balanced chemical equation,

$1$ mole of

$ROH$ reacts with

$1$ mole of

$PBr_3$ to form

$1$ mole of

$RBr$

Example:

$3CH_3CH_2OH +PBr_3\xrightarrow{P+Br_2} 3CH_3CH_2Br + H_3PO_3$

Which of the following alcohols will react with

${H}^{+}$ with greatest ease?

The relative lowering of the vapour pressure of an aqueous solution containing a non-volatile solute is 0.The molality of the solution is:

0%
0.70
0%
0.30
0%
0.125
0%
0.07

Explanation

$\bf{Explanation-}$

From Roult's law, relative lowering of vapour pressure is given by

$\dfrac{P^\circ - P_s}{P^\circ} = X_{solute}$
Where,

$P^\circ$ = Vapour pressure of solvent

$P_s$ = Vapour pressure of solution

$\dfrac{P^\circ - P_s}{P^\circ}$ = Relative lowering of vapour pressure

Thus,

$X_{solute} = 0.0125$

$X_{solute} = \dfrac {mM}{1000 + mM}$

Where, m= molarity and M = molar mass of aqueous solution.

$0.0125 = \dfrac{m \times 18}{1000 + m \times 18}$

$12.5 + 0.225 m = 18 \times m$

$18 m - 0.225 m =12.5$

$m = \dfrac{12.5} {17.775}$

$m = 0.70$
So, morality of the solution is

$0.70 \ m$

$\bf{Conclusion-}$ Hence, option A is correct.

Hydroboration oxidation of 2-methyl but-1-ene gives _____.

0%
$2-methyl \ butan-1-ol$
0%
$2-methyl\ butan-2-ol$
0%
$2-methyl\ butan-1, 2-diol$
0%
$2-methyl\ butan-1, 3-diol$

Structure of

$C_3H_7Br$ should be

0%
0%
0%
Both of these
0%
None of these

Predict the major products (A) and (B).

Explanation

On treatment of

$OMDM$ ,the product will be trans and cis. But when treated by

${ H }_{ 3 }{ O }^{ \oplus }$ ion it will not produce cis trans product.
1137159_1198848_ans_9c430bec04114f06a45f281fd5848e1f.png

In the reaction, the product

$A$ is:

Which of the following exhibit highest boiling point?

Explanation

Primary alcohol easily forms hydrogen bonds with water than 2

$^{o}$ and 3

$^{o}$ alcohols thus 1

$^{o}$ alcohol has more boiling point than 3

$^{o}$ and 2

$^{o}$ .

The image of the compound shown in the figure is a 1

$^0$ alcohol, so, it has more boiling point.

Hence, the correct option is

$B$

1123541_1186831_ans_ed45d5644c70451da69f4c4013ce5860.png

Which of the following is a secondary alcohol ?

0%
0%
0%
0%
${ CH }_{ 3 }OH\quad$

Explanation

Alcohols can be classified as primary, secondary or tertiary on the basis of the nature of the carbon to which the OH group is attached. This carbon is called carbinol carbon.

Primary alcohol - The carbinol carbon is attached to only one other carbon atom. Example: 1-hexanol

Secondary alcohol – The carbinol carbon is attached to two other carbon atoms. Example: 2-hexanol

Tertiary alcohol - The carbinol carbon is attached to three other carbon atoms. Example: 2-methyl-2-pentanol

$(CH_3)_2CH-OH$ Option B is a secondary alcohol.

Whereas Option A is a primary alcohol, Option C is tertiary alcohol, Option D is a primary alcohol

Option B is the correct answer.

The product A and B respectively are:

0%
0%
0%
0%
no formation of A and B

Which compound is formed when a mixture of calcium acetate and calcium formate if heated ?

0%
$H_3C-\overset{O}{\overset{||}{C}}-CH_3$
0%
$H_3C-\overset{O}{\overset{||}{C}}-O-C-CH_3$
0%
$HCHO$
0%
$H_3C-CHO$

Write the IUPAC name of the following compounds.

0%
1-methoxy-3-nitrocyclohexane
0%
3-methoxy-1-nitrocyclohexane
0%
1-nitro-3-methoxycyclohexane
0%
3-nitro-1-methoxycyclohexane

In which of the following substances, ethanol is not used?

0%
Tonics
0%
Cough mixture
0%
Candle
0%
Alcohol

But-2-ene can be obtained by reacting:

0%
1,2-dibromopropane with zinc
0%
Ethyl bromide with sodium
0%
Ethylidene bromide with zinc
0%
n-butyl alcohol with alcoholic KOH

The IUPAC name of the following compound is :

$CH_3 - \overset{CH_3\!\!\!\!\!}{\overset{|}{CH}} - \overset{O}{\overset{||}{C}} - CH_2 - CH_2 OH$

0%
$1$ -hydroxy- $4$ -methylpentan- $3$ -one
0%
$2$ -methyl- $5$ -hydroxypentan- $3$ -one
0%
$4$ -methyl- $3$ -oxopentan- $1$ -ol
0%
hexan- $1$ -ol- $3$ -one

Which of the following compounds when heated with CO at

$150^oC$ and 500 atm pressure in presence of

$BF_3 ,$ forms ethyl propionate ?

0%
$C_2H_5OH$
0%
$CH_3OCH_3$
0%
$C_2H_5OC_2H_5$
0%
$CH_3OC_2H_5$

Consider the given reaction
Identify alkene.

0%
$CH_{3} - CH_{2} - CH = CH_{2}$
0%
$CH_{3} - CH = CH - CH_{3}$
0%
$(CH_{3})_{2}C = C(CH_{3})_{2}$
0%
$CH_{3} - CH = \underset {\underset {CH_{3}}{|}}{C} - CH_{3}$

$A + CCl_4 + KOH \rightarrow$ Salicylic acid
'A' in above reaction is

Explanation

Phenol with

$CCl_4$ and KOH gives salicylic acid. The reaction is known as Reimer - Tiemann reaction.

so unknown A is phenol

given A option is correct answer

Ethene on reaction with cold & dilute alkaline

$KMnO_4$ gives ?

0%
Ethylene glycol
0%
Propylene glycol
0%
Acetone
0%
Alcohol

Identify the correct order of boiling points of the following compounds:

$CH_3CH_2CH_2CH_2OH$ (1)

$CH_3CH_2CH_2CHO$ (2)

$CH_3CH_2CH_2COOH$ (3)

0%
1>2>3
0%
3>1>2
0%
1>3>2
0%
3>2>1

Which of the following combinations can be used for the preparation of cis vic diol?

0%
Alkene, Baeyer reagent
0%
Alkene , $OsO_{4}$
0%
Alkene, MMPP and $H_{2}O/H$
0%
Both of (A) and (B)

Give the IUPAC name of the above compound.

0%
2-Bromo 3-methyl butyric acid
0%
2-Bromo 4-formyl butane
0%
3-Bromo 2-methyl butanoic acid
0%
None of the above

The compounds A and B are mixed in equimolar proportion to from the product,

$A+B \rightleftharpoons C +D$ . AT equilibrium, one third of A and B are consumed.The equilibrium constant for the reaction is _______.

0%
0.5
0%
4.0
0%
2.5
0%
0.25

The compounds A and B in the following reaction are ________ respectively.

0%
A = Benzyl alcohol, B = Benzyl cyaninde
0%
A = Benzyl chloride, B = benzyl cyanide
0%
A = benzyl alcohol, B = Benzyl isocyanide
0%
none of these

$3-methyl-1-butene$ on oxymercuration -demercuration yields________ as the major product

0%
$3-methyl-2-butanol$
0%
$2-methyl-2-butanol$
0%
$3-methyl-1-butanol$
0%
$2-methyl-1-buranol$

Which of the following name does not fit a real name?

0%
$3$ -methyl $3$ -hexanone
0%
$4$ -methyl $3$ -hexanone
0%
$3$ -methyl $3$ -hexanol
0%
$2$ -methylcyclohexanone

IUPAC name of compound is:

0%
5-ethyl-3,3-dimethyl cyclohex-en-6-ol
0%
6-Ethyl-4,4-dimethyl cyclohex-2-en-1-ol
0%
2-ethyl-4,4-dimethyl cyclohex-en--enol
0%
6-ethyl-4,4-dimethyl cyclohexenol

Arrange above structures in increasing order of acidic strength.

0%
$I<II<III$
0%
$I<III<II$
0%
$II<I<III$
0%
$II<III<I$

Correct order of acidic strength.

0%
$I > II > III$
0%
$II > III > I$
0%
$I > III > II$
0%
$III > II > I$

Explanation

Acidic nature

$\alpha - I$ .
1273915_1630428_ans_1eabeaaa7b6341cc89528ee93adcdd91.jpg

Three chemical reactions are shown.
1 catalytic addition of steam to ethene
2 combustion of ethanol
3 fermentation of glucose
In which of the reactions does the relative molecular mass of the carbon-containing compound
decrease?