Class 11th

Benzene is a rich source of electrons because of the presence of an electron cloud containing 6 n-electrons above and below the plane of the ring. Consequently, it attracts the electrophiles (electron-deficient) reagents towards it and repels nucleophiles (electron- rich) reagents. As a result, benzene undergoes electrophilic substitution reactions easily and nucleophilic substitutions with difficulty.

3.44.  (d) Assertion is a wrong statement. Non-metallic elements have a strong tendency to gain electrons. Therefore, electronegativity is directly related to those non-metallic properties of elements. It can be further extended to say that the electronegativity is inversely related to the metallic properties of elements.

Thus, the increase in electronegativities across a period is accompanied by an increase in non-metallic properties (or a decrease in metallic properties) of elements

The hybridization state of carbon in these three compounds is:

Since s-electrons are closer to the nucleus, therefore, as the s-character of the orbital making the C—H bond increases, the electrons of C—H bond lie closer and closer to the carbon atom. In other words, the partial +ve charge on the H-atom and hence the acidic character increases as the s-character of the orbital increases. Thus, the acidic character decreases in the order: Ethyne > Benzene > Hexane.

o-Xylene may be regarded as a resonance hybrid of the following two Kekule structures. Ozonolysis of each one of these gives two products as shown below:

Thus, in all, three products are formed. Since all the three products cannot be obtained from any one of the two Kekule structures, this shows that o-xylene is a resonance hybrid of the two Kekule structures (I and II).

Branching of carbon atom chain decreases the boiling point of alkane.

The expanded formula of the given compound is

3.42. (a) Elements of the same group have similar valence shell electronic configuration and, therefore, exhibit similar chemical properties. However, the elements of the same period have an incrementally increasing number of electrons from left to right, and, therefore, have different valences.