General Organic Chemistry MCQ Questions & Answers in Organic Chemistry | Chemistry
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101.
IUPAC name of the compound is
A
$$trans-3- iodo-4-chloro-3-pentene$$
B
$$cis-2-chloro-3-iodo-2-pentene$$
C
$$trans-2-chloro-3-iodo-2-pentene$$
D
$$cis-3-iodo-4-chloro-3-pentene$$
Answer :
$$trans-2-chloro-3-iodo-2-pentene$$
In this compound groups preferential order is $$ - Cl > - C{H_3}\,{\text{and}}\, - I > - C{H_2} - C{H_3}$$
Hence, more preferential order containing groups are attached at opposite sides. So, it is $$E$$ $$(trans)$$ - isomer. Thus, its name is $$trans-2-chloro-3-iodo-2-pentene.$$
102.
Electrophilic addition reactions proceed in two steps. The first step involves the addition of an electrophile. Name the type of intermediate formed in the first step of the following addition reaction.
$${H_3}C - HC = C{H_2} + {H^ + } \to ?$$
A
$${2^ \circ }$$ Carbanion
B
$${1^ \circ }$$ Carbocation
C
$${2^ \circ }$$ Carbocation
D
$${1^ \circ }$$ Carbanion
Answer :
$${2^ \circ }$$ Carbocation
Thus, $${2^ \circ }$$ carbocation is formed.
103.
Glycerine can be purified by
A
vacuum distillation
B
simple distillation
C
steam distillation
D
fractional distillation
Answer :
vacuum distillation
No explanation is given for this question. Let's discuss the answer together.
104.
Which one of the following compounds will be most easily attacked by an electrophile?
A
B
C
D
Answer :
$$ - Cl{\text{ - }}atom$$ shows $$+R$$ - effect that $$o/p$$ -directive influence but deactivate the benzene ring. While $$ - OH, - C{H_3}$$ group also shows $$o/p$$ -influence but activate the benzene ring. But in these $$-OH$$ group activates more than $$ - C{H_3}.$$
Hence, order of electrophilic substitution is
105.
The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in vapour phase. A suitable method for the extraction of these oils from the flowers is
A
distillation
B
crystallisation
C
distillation under reduced pressure
D
steam distillation
Answer :
steam distillation
Steam distillation is used to separate substances which are steam volatile and are immiscible with water.
106.
The radical is aromatic because it has
A
$$6p$$ - orbitals and 6 unpaired electrons
B
$$7p$$ - $$2$$ orbitals and 6 unpaired electrons
C
$$7p$$ - orbitals and 7 unpaired electrons
D
$$6p$$ - orbitals and 7 unpaired electrons
Answer :
$$7p$$ - orbitals and 7 unpaired electrons
Because of the presence of $$7$$ $$p$$ - orbitals and 7 unpaired electrons, it is aromatic in nature as these unpaired electrons delocalise in $$p$$ - orbitals.
107.
The enol form of acetone after treatment with $${D_2}O$$ gives :
A
B
C
D
Answer :
The enol form of acetone is with $${D_2}O$$ it gives
108.
Which of the following numberings is correct ?
A
$$A$$
B
$$B$$
C
$$C$$
D
$$D$$
Answer :
$$D$$
The numbering of $$C$$ - atom starts from $$\mathop C\limits^ * $$ or $$\mathop C\limits^{ * * } .$$ But numbering from $$\mathop C\limits^ * $$ give minimum locant $$(2)$$ to $$Br$$ which is correct.
109.
Which nomenclature is not according to IUPAC system?
A
B
C
D
Answer :
In IUPAC system of nomenclature, preference is given to multiple bond than halogen substituent, so the correct name of $$Br - \mathop {\mathop {C{H_2}}\limits^3 - \mathop {CH}\limits^2 = \mathop {C{H_2}}\limits^1 }\limits_{3{\text{ }} - bromoprop - 1 - ene} $$ is Priority is given to double bond than halogen.
110.
The correct IUPAC name of the compound is
A
4-formyl-2-oxocyclohexanecarboxylic acid
B
4-carboxy-2-oxocyclohexanal
C
4-carboxy-1-formylcyclohexanone
D
2-carboxy- 5-formyl-1-oxocyclohexane
Answer :
4-formyl-2-oxocyclohexanecarboxylic acid
Priority of functional groups is
Hence, the IUPAC name is 4-formyl-2-oxocyclohexane carboxylic acid.