Question 1

Which one of the following series contains only electrophiles?

Accepted Answer

Electrophiles are electron-deficient species that can accept an electron pair. They are either positively charged or neutral molecules with an incomplete octet or highly polar bonds. In the first series, R-OH and NH _3 have lone pairs on oxygen and nitrogen respectively, making them nucleophiles. In the second series, H _2 O and R _2 N ^- have lone pairs and a negative charge respectively, making them nucleophiles. In the third series, BF _3 is an electron-deficient Lewis acid with an incomplete

Question 2

Which of the following molecule has Chiral Carbon?

Accepted Answer

A chiral carbon atom is one that is bonded to four different atoms or groups. Let us examine each option: In the first molecule, the central carbon is bonded to two identical hydrogen (H) atoms. Thus, it is achiral. In the second molecule, the central carbon is bonded to four different groups: H, CH_3, OH, and I. Thus, it is a chiral carbon. In the third molecule, the central carbon is bonded to two identical methyl (CH_3) groups. Thus, it is achiral. In the fourth molecule, the central carbon i

Question 3

The IUPAC name of the following compound is,

Accepted Answer

The parent ring in the given structure is cyclohexane. The substituents attached to the ring are one methoxy group (-OCH_3) and two ethyl groups (-CH_2CH_3). According to IUPAC nomenclature rules, the ring must be numbered to give the lowest possible set of locants for the substituents. If we start numbering from the carbon with the two ethyl groups, the locant set is 1, 1, 4. If we start numbering from the carbon with the methoxy group, the locant set is 1, 4, 4. Comparing the two sets, (1, 1,

Question 4

What is IUPAC name of the following compound ?

Accepted Answer

The principal functional group in the given compound is the amine (-NH_2) group. The longest continuous carbon chain containing the carbon attached to the amine group and the double bond has 5 carbon atoms, making the parent chain a pentene. According to IUPAC rules, the chain is numbered to give the principal functional group the lowest possible locant, as the amine group has higher priority than the alkene double bond. Numbering from right to left places the amine group at position 2 and the d

Question 5

Which of the following is tertiary benzylic alcohol?

Accepted Answer

A benzylic alcohol has the -OH group attached to a carbon atom that is directly bonded to a benzene ring (benzylic carbon). For the alcohol to be tertiary (3^ ), the benzylic carbon must be bonded to three other carbon atoms (one from the benzene ring and two other alkyl groups). Let us analyze the given options: Option (326143): The structure is benzyl alcohol (Ph-CH_2-OH). The benzylic carbon is bonded to only one carbon atom (from the benzene ring). It is a primary (1^ ) benzylic alcohol. Opt

Question 6

Which from following is a correct priority order for selection of principal functional group for nomenclature of polyfunctional compound according to IUPAC system ?

Accepted Answer

According to the IUPAC nomenclature rules for polyfunctional compounds, the priority order of functional groups for selecting the principal functional group is: Carboxylic acids > Sulfonic acids > Esters > Acid halides > Amides > Nitriles > Aldehydes > Ketones > Alcohols > Amines > Alkenes > Alkynes. Comparing the given functional groups, the correct priority order is: - CONH _2 > - CHO > - OH > - C C - Answer: - CONH _2 > - CHO > - OH > - C C -

Question 7

What is IUPAC name of following compound?

Accepted Answer

The principal functional group in the given compound is the carboxylic acid group (-COOH). Therefore, the parent chain is taken as benzoic acid. Numbering of the benzene ring starts from the carbon atom attached to the -COOH group as position 1. To give the lowest possible number to the substituent, the carbon attached to the methyl group (-CH_3) is numbered as 2. Thus, there is a methyl group at the 2-position of the benzoic acid ring. The IUPAC name of the compound is 2-Methylbenzoic acid. (No

Question 8

Find the number of structural isomers possible for hexane ?

Accepted Answer

The molecular formula of hexane is C_6H_ 14 . The possible structural isomers are: 1. CH_3-CH_2-CH_2-CH_2-CH_2-CH_3 (n-hexane) 2. CH_3-CH(CH_3)-CH_2-CH_2-CH_3 (2-methylpentane) 3. CH_3-CH_2-CH(CH_3)-CH_2-CH_3 (3-methylpentane) 4. CH_3-C(CH_3)_2-CH_2-CH_3 (2,2-dimethylbutane) 5. CH_3-CH(CH_3)-CH(CH_3)-CH_3 (2,3-dimethylbutane) Thus, there are five structural isomers possible for hexane. Answer: Five

Question 9

Which of the following is NOT a phenol ?

Accepted Answer

A phenol is a compound in which a hydroxyl group (-OH) is directly attached to an sp^2 hybridized carbon atom of an aromatic ring. In the first option, the -OH group is directly attached to the benzene ring (o-nitrophenol), so it is a phenol. In the second option, the -OH group is directly attached to the naphthalene ring (2-naphthol), so it is considered a phenolic compound. In the third option, the -OH group is directly attached to the benzene ring (o-bromophenol), so it is a phenol. In the fo

Question 10

Which from following structures represents 1,3 butadiene ?

Accepted Answer

The IUPAC name 1,3-butadiene corresponds to a four-carbon chain with two double bonds located at the 1st and 3rd carbon atoms. The chemical formula is CH_2=CH-CH=CH_2. Let us analyze the given bond-line structures: 1. The first structure has a five-carbon chain with one double bond at the second position, representing pent-2-ene. 2. The second structure has a four-carbon chain with double bonds at the first and third positions, representing 1,3-butadiene. 3. The third structure has a four-carbon

Question 11

IUPAC name of glycerol is -

Accepted Answer

The chemical formula of glycerol is CH_2(OH)-CH(OH)-CH_2(OH). The principal functional group is the hydroxyl group (-OH), which is indicated by the suffix 'ol'. The longest carbon chain containing the -OH groups has 3 carbon atoms, so the parent alkane is propane. Numbering the carbon chain from either end gives the positions of the -OH groups as 1, 2, and 3. Since there are three hydroxyl groups, the multiplier 'tri' is used. Combining these parts, the IUPAC name of glycerol is propane-1,2,3-tr

Question 12

Which among the following is allylic halide ?

Accepted Answer

Allylic halides are compounds in which the halogen atom is bonded to an sp^3 hybridized carbon atom adjacent to a carbon-carbon double bond (C=C). In CH _2 = CH - CH _2 - X , the halogen atom X is attached to the sp^3 hybridized carbon atom which is directly attached to the C=C double bond. Thus, it is an allylic halide. CH _3 - CH _2 - CH _2 - X is a primary alkyl halide. C _6 H _5 CH _2 - X is a benzylic halide. CH _3 - CH = CH - X is a vinylic halide. Answer: CH _2 = CH - CH _2 - X

Question 13

What is IUPAC name of the following compound ?

Accepted Answer

To find the IUPAC name of the given compound, we follow these steps: 1. Identify the principal functional group: The molecule contains a hydroxyl group (-OH) and a double bond. The hydroxyl group has higher priority, so it is the principal functional group and must be given the lowest possible locant. 2. Determine the longest carbon chain: The longest continuous carbon chain that contains both the -OH group and the double bond must be selected. Tracing from the rightmost ethyl group to the leftm

Question 14

Which among the following is an aromatic aldehyde ?

Accepted Answer

An aromatic aldehyde is a compound in which the aldehyde group ( -CHO ) is directly attached to an aromatic ring. Let us evaluate the given options: 1. In the first structure (3-phenylpropanal), the -CHO group is attached to an sp^3 hybridized carbon of an aliphatic chain, not directly to the benzene ring. 2. In the second structure (cinnamaldehyde), the -CHO group is attached to an sp^2 hybridized carbon of an alkene chain. 3. In the third structure (cyclohexanecarbaldehyde), the -CHO group is

Question 15

Which from the following aldehydes contains two - CHO groups in a molecule?

Accepted Answer

Acrolein is CH _2= CH - CHO , which contains one - CHO group. o-Tolualdehyde is o- CH _3- C _6 H _4- CHO , which contains one - CHO group. Phthaldehyde is benzene-1,2-dicarbaldehyde, C _6 H _4( CHO )_2, which contains two - CHO groups. Butyraldehyde is CH _3- CH _2- CH _2- CHO , which contains one - CHO group. Therefore, phthaldehyde contains two - CHO groups. Answer: Phthaldehyde

Question 16

Which from following is a primary benzylic alcohol?

Accepted Answer

A benzylic alcohol contains an -OH group attached to an sp^3 hybridized carbon atom directly bonded to an aromatic ring. A primary alcohol has the -OH group attached to a primary carbon atom (a carbon bonded to only one other carbon). In C _6 H _5 CH _2 OH , the -OH group is attached to a CH _2 group which is directly bonded to the benzene ring. Thus, it is a primary benzylic alcohol. In C _6 H _5 CH ( OH ) CH _3, the -OH group is attached to a secondary carbon, making it a secondary benzylic al

Question 17

Identify the aldehyde from following so that the aldehydic group is NOT attached with any sp^3 hybrid 'c' atom.

Accepted Answer

Methanal is H-CHO. The aldehydic group (-CHO) is attached to a hydrogen atom, not to any carbon atom. Therefore, it is not attached to any sp^3 hybridized carbon atom. Ethanal is CH_3-CHO. The -CHO group is attached to a methyl group, which contains an sp^3 hybridized carbon atom. 2-Methylpropanal is (CH_3)_2CH-CHO. The -CHO group is attached to a CH group, which is an sp^3 hybridized carbon atom. Propanal is CH_3-CH_2-CHO. The -CHO group is attached to a CH_2 group, which is an sp^3 hybridized

Question 18

What is the number of chiral carbon atoms in 2-chlorobutane?

Accepted Answer

The structure of 2-chlorobutane is CH_ 3 -CH(Cl)-CH_ 2 -CH_ 3 . A chiral carbon atom is one that is bonded to four different atoms or groups. In 2-chlorobutane, the second carbon atom (C2) is bonded to four different groups: a hydrogen atom (-H), a chlorine atom (-Cl), a methyl group (-CH_ 3 ), and an ethyl group (-CH_ 2 CH_ 3 ). Therefore, C2 is a chiral carbon. The other carbon atoms (C1, C3, and C4) are bonded to at least two identical hydrogen atoms, so they are not chiral. Thus, there is on

Question 19

Which from following compounds does NOT contain double bond in it ?

Accepted Answer

Tetrahydrofuran is a fully saturated five-membered cyclic ether with the chemical formula C_4H_8O. It does not contain any double bonds. 4H-Pyran is a six-membered non-aromatic heterocyclic compound containing one oxygen atom and two double bonds. Pyrrole is a five-membered aromatic heterocyclic compound containing one nitrogen atom and two double bonds. Thiophene is a five-membered aromatic heterocyclic compound containing one sulfur atom and two double bonds. Therefore, tetrahydrofuran is the

Question 20

Which from following compounds is NOT optically active?

Accepted Answer

The optical activity of a compound depends on the presence of a chiral carbon atom, which is bonded to four different groups. In 3-bromohexane, the C3 carbon is bonded to a hydrogen atom, a bromine atom, an ethyl group, and a propyl group. Since all four groups are different, it is chiral and optically active. In 2-bromo-2-methylbutane, the C2 carbon is bonded to a bromine atom, an ethyl group, and two identical methyl groups. Since two groups are the same, it does not have a chiral center and i

General Organic Chemistry — Previous Year Questions & Solutions