General Organic Chemistry MCQ Questions & Answers in Organic Chemistry | Chemistry
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221.
The correct order of decreasing acidic strength of trichloroacetic acid $$(A),$$ trifluoroacetic acid $$(B),$$ acetic acid $$(C)$$ and formic acid $$(D)$$ is
A
$$B > A > D > C$$
B
$$B > D > C > A$$
C
$$A > B > C > D$$
D
$$A > C > B > D$$
Answer :
$$B > A > D > C$$
If an electron withdrawing group ( $$-I$$ - showing group ) is present, e.g. $$ - C{F_3}$$ has more ( $$-I$$ - effect ) withdrawing power than $$ - CC{l_3},$$ it makes the removal of proton more easy by stabilising the remaining carboxylate ion and thus, makes the acid more acidic.
The order of acidity of given compounds is
222.
The correct representation of 4-hydroxy-2-methylpent-2-en-1-al is
A
B
C
D
Answer :
223.
Allyl isocyanide has :
A
$$9\sigma \,{\text{and}}\,4\pi \,{\text{bonds}}$$
B
$$8\sigma \,{\text{and}}\,5\pi \,{\text{bonds}}$$
C
$$9\sigma ,3\pi \,{\text{and}}\,2\,{\text{non - }}\,{\text{bonds}}\,{\text{electrons}}$$
D
$$8\sigma ,3\pi \,{\text{and}}\,4\,{\text{non - }}\,{\text{bonds}}\,{\text{electrons}}$$
$$C{H_2} = CH - C{H_2} - N\mathop = \limits^ \to C:$$
The above structure of allyl isocyanide clearly shows $$5C - H\left( \sigma \right),2C - C\left( \sigma \right),1C - N\left( \sigma \right),1N - C\left( \sigma \right),1C - C\left( \pi \right),2N - C\left( \pi \right)$$ bonds, i.e., $$9\sigma $$ and $$3\pi $$ bonds in all. There are 2 non-bonded electrons on the C-atom (co-ordinate bond between $$N$$ and $$C,$$ the electron pair of $$N$$ is shifted towards $$C$$ ) .
224.
The IUPAC name for \[C{{H}_{3}}-\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{2}}-\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{C}}\,-OH\] is _________.
A
1-hydroxypentane-1, 4-dione
B
1, 4-dioxopentanol
C
1-carboxybutan-3-one
D
4-oxopentanoic acid
Answer :
4-oxopentanoic acid
225.
Geometrical isomers differ in
A
position of functional group
B
position of atoms
C
spatial arrangement of atoms
D
length of carbon chain
Answer :
spatial arrangement of atoms
Geometrical isomers The isomers having same molecular formula but differ in the position of atoms or groups in space due to hindered rotation about a double bond.
226.
How many chain isomers could be obtained from the alkane, $${C_6}{H_{14}}?$$
A
Four
B
Five
C
Six
D
Seven
Answer :
Five
Hexane $$\left( {{C_6}{H_{14}}} \right)$$ has five chain isomers and these are
227.
The IUPAC name of the compound having formula is
A
3, 3, 3-trimethylprop-1-ene
B
1, 1, 1-trimethylprop-2-ene
C
3, 3-dimethylpent-1-ene
D
2, 2-dimethylbut-3-ene
Answer :
3, 3-dimethylpent-1-ene
3, 3-Dimethylpent-1-ene
228.
The distillation technique most suited for separating glycerol from spent-lye in the soap industry is :
A
Steam distillation.
B
Distillation under reduced pressure.
C
Simple distillation
D
Fractional distillation
Answer :
Distillation under reduced pressure.
Spent-lye and glycerol are separated by distillation under reduced pressure.
Under the reduced pressure the liquid boil at low temperature and the temperature of decomposition will not reach. e.g. glycerol boils at $${290^ \circ }C$$ with decomposition but at reduced pressure it boils at $${180^ \circ }C$$ without decomposition.
229.
Among the following compound one that is most reactive towards electrophilic nitration is
A
benzoic acid
B
nitrobenzene
C
toluene
D
benzene
Answer :
toluene
Presence of electron releasing groups like $$-R,-OH,$$ etc. increases the electron density at $$o/p$$ - position and thus, makes the benzene ring more reactive ( at $$o/p$$ - positions ) towards an electrophile. On the other hand, electron withdrawing groups like $$ - COOH, - N{O_2},$$ etc. if present, reduces electron density and thus, reduces the activity of benzene nucleus towards an electrophile. Thus, the order of the given compounds towards electrophilic nitration is
Thus, toluene is most reactive towards electrophilic nitration.
230.
Which of the following would react most readily with nucleophiles ?
A
B
C
D
Answer :
Aryl halides do not undergo nucleophilic substitution under ordinary conditions. The low reactivity of halogen atom in aryl halides is due to resonance. However, aryl halides can be made to undergo nucleophilic substitution either under drastic condition ( high temperature, pressure or very strong nucleophiles ) or by activating the nuclear halogen by introducing electron withdrawing group e.g. $$N{O_2}, - CHO,CN$$ etc. in the $$o - $$ and $$p - $$ position to the nuclear halogen. Hence, $$p - $$ nitrochlorobenzene would react most readily with nucleophiles.