Q: In \$C_{6}H_{14}\$, the number of possible structural isomers is:

\$C_6H_{14}\$ is hexane. It has 5 structural isomers viz. n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane.

Q: The number of isomers in \$C_{4}H_{10}O\$ are:

There are seven isomers in \$C_{4}H_{10}O\$. Out of these seven isomers, four are alcohol and three are ether.

Q: How many structure isomers can you draw for pentane?

Pentane (\$C_5H_{12}\$) is an organic compound and an alkane with five carbon atoms. Pentane has three structural isomers. These are n-pentane, Iso-pentane and neo-pentane. Pentane means exclusively the n-pentane isomer; the other two being called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane. Structures of all the three isomers are given here.Option B is correct.

Q: Identify electrophilic centre in the following:1. \$C{H}_{3}CH = O\$2. \$C{H}_{3} - CN\$3. \$C{H}_{3}I\$

Among \$C{ H }_{ 3 }\overset { \downarrow }{ C } H = O, { H }_{ 3 }C - \overset { \downarrow }{ C } \equiv N\$, and \${ H }_{ 3 }\overset { \downarrow }{ C } - I\$, the arrow-marked \$C\$ atoms are electrophilic centers, as they will have partial positive charge due to the polarity of bond.Hence, they can accept electrons from nucleophile.

Question 1

What is a homologous series? State any four characteristics of a homologous series?

Accepted Answer

Homologous series is a series of compounds with similar chemical properties and the same functional group differing from the successive member by $-CH_2$.Example: The homologous series of straight-chain alkanes can be represented by the general formula $C_nH_{2n+2}$Thus the first four members of alkane homologous series are  $\displaystyle CH_4$ (methane),  $\displaystyle CH_3-CH_3$ (Ethane),  $\displaystyle CH_3-CH_2-CH_3$ (propane) and  $\displaystyle CH_3-CH_2-CH_2-CH_3$ (butane). Characteristics of a homologous series are:(i) Each member of the series can be represented by a general formula.(ii) All the members of the series can be prepared by the same general methods.(iii) Physical properties change throughout the series in a regular way.(iv) Members of homologous series have similar chemical properties.

Question 2

In $C_{6}H_{14}$, the number of possible structural isomers is:

Accepted Answer

$C_6H_{14}$ is hexane. It has 5 structural isomers viz. n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane.

Question 3

The number of isomers in $C_{4}H_{10}O$ are:

Accepted Answer

There are seven isomers in $C_{4}H_{10}O$. Out of these seven isomers, four are alcohol and three are ether.

Question 4

What are electrophiles and nucleophiles ? Explain with examples.

Accepted Answer

Electrophiles are electron deficient species and can accept an electron pair from electron rich species.Examples include carbocations and carbonyl compounds. A nucleophile is electron rich species and donates electron pairs to electron deficient species. Examples include carbanions, water , ammonia, cyanide ion etc.

Question 5

Write any 4 characteristic features of homologous series of organic compounds?

Accepted Answer

Characteristics are :The members of the homologous series have same functional group.Members have the same general formula.Members have the almost same chemical properties due to same functional group.Members have common general method of preparation.

Question 6

How many structure isomers can you draw for pentane?

Accepted Answer

Pentane ($C_5H_{12}$) is an organic compound and an alkane with five carbon atoms. Pentane has three structural isomers. These are n-pentane, Iso-pentane and neo-pentane. Pentane means exclusively the n-pentane isomer; the other two being called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane is not an isomer of pentane. Structures of all the three isomers are given here.Option B is correct.

Question 7

Which of the following compounds will exhibit geometrical isomerism?

Accepted Answer

1-phenyl-2-butene shows geometrical isomerism in the form of cis and trans isomers.However, the geometrical isomerism is not possible for 3-phenyl-1-butene, 2-phenyl-1-butene and 1,1-diphenyl-1-propane.

Question 8

Which of the following is not electrophile?

Accepted Answer

In ammonia, nitrogen atom has lone pair electron which works as electron donar so ammonia molecule is a nucleophile.All else are electrophile here.

Question 9

Hyperconjugation involves overlap of which of the following orbitals?

Accepted Answer

Hyper conjugation involves overlap of p orbitals. It is the interaction of the electrons in a sigma bond (usually CH or CC) with an adjacent empty (or partially filled) non-bonding p-orbital, anti bonding or orbital, or filled orbital, to give an extended molecular orbital that increases the stability of the system.

Question 10

Identify electrophilic centre in the following:1.  $C{H}_{3}CH = O$2.  $C{H}_{3} - CN$3.  $C{H}_{3}I$

Accepted Answer

Among $C{ H }_{ 3 }\overset { \downarrow  }{ C } H = O,  { H }_{ 3 }C - \overset { \downarrow  }{ C } \equiv N$, and ${ H }_{ 3 }\overset { \downarrow  }{ C } - I$, the arrow-marked $C$ atoms are electrophilic centers, as they will have partial positive charge due to the polarity of bond.Hence, they can accept electrons from nucleophile.