Most stable carbocation is:

${\mathrm{pK}}_{\mathrm{a}}$ value of the compound decreases if X is:

Arrange the following in correct order of acidic strength:

$\left(\mathrm{I}\right) {\mathrm{CH}}_3-{\mathrm{NO}}_2$

$\left(\mathrm{II}\right) {\mathrm{NO}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{NO}}_2$

$\left(\mathrm{III}\right) {\mathrm{CH}}_3 - {\mathrm{CH}}_2 - {\mathrm{NO}}_2$

$\left(\mathrm{IV}\right) {\mathrm{NO}}_2—{\mathrm{CH}}_2—{\mathrm{NO}}_2$

In which of the following species, incorrect direction of Inductive effect is/are shown?

Place the following in the correct order of acidity.

$\mathrm{CH}\equiv \mathrm{C}-\mathrm{COOH} ; {\mathrm{CH}}_2=\mathrm{CH}-\mathrm{COOH} ; {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{COOH}$

Which of the following statements is/are correct for the inductive effect?

The correct orders and statements for histidine are

Give the stability order in the following pairs.

Give the stability order in the following pairs: