Which of the following cannot exist at room temperature?

Based upon an understanding of product stability,predict the product formed when the following dianion reacts with one equivalent of acid $(H^+)$.

The order of circled $C-H$ bond dissociation energy in the following compounds is:

Which of the following species is paramagnetic in nature?

Homolytic fission of the following alkanes forms free radicals: $CH_3-CH_3$,$CH_3-CH_2-CH_3$,$(CH_3)_2CH-CH_3$,and $CH_3-CH_2-CH(CH_3)_2$. The increasing order of stability of the resulting free radicals is:

Stability order of the following carbocations:
$(i) CH_3 - C^{+}(OCH_3) - CH_3$
$(ii) CH_3 - C^{+}(CH_3) - CH_3$
$(iii) CH_3 - NH - C^{+}H_2$
$(iv) CH_3 - C^{+}H_2$