Answer
Verified
379.8k+ views
Hint:The p-nitrophenol is a nitro group attached to the para position of phenol. Similarly, p-cresol is a methyl group attached to the para position of phenol. An electronegative atom pulls the electrons and has high electron density. The presence of the electron-withdrawing group and electron-donating group affects the acidity of the compounds. Acidity is determined by the ability to release ${{\text{H}}^{\text{ + }}}$ ions.
Complete step by step answer:
Let us look at the structure of p-nitrophenol. Phenol is an electron-deficient group.
This is the lewis dot structure of ${\text{N}}{{\text{O}}_{\text{2}}}$.
We can see that Nitrogen in ${\text{N}}{{\text{O}}_{\text{2}}}$ already has a positive charge on it. It is because it gave one of its lone pairs to oxygen (double bond). When this nitrogen is attached to the benzene ring, the nitrogen will pull the electrons from the benzene ring to reduce the positive charge.
Therefore, ${\text{N}}{{\text{O}}_{\text{2}}}$ is an electron-withdrawing group.
In p-nitrophenol, since it is ${\text{N}}{{\text{O}}_{\text{2}}}$ is an electron-withdrawing group, all the electron density will be drifted towards ${\text{N}}{{\text{O}}_{\text{2}}}$
This will result in a decrease in the electron density of oxygen in the O-H bond.
Thus, the release of ${{\text{H}}^{\text{ + }}}$ is easier.
Now, let us look at o-cresol.
The ${\text{ - C}}{{\text{H}}_{\text{3}}}$ is attached to the para position of phenol.
We know that the methyl group in cresol is electron-donating. It gives its electron density to the electron-deficient phenol. Thus, the electron density on the O-H group increases.
Therefore, it cannot give out ${{\text{H}}^{\text{ + }}}$ ions.
Therefore, the correct answer is that the ${\text{ - N}}{{\text{O}}_{\text{2}}}$ decreases the electron density on the oxygen of the O-H group making p-nitrophenol a stronger acid.
Thus, the correct option is (B).
Note: The presence of an electron-donating group will decrease the acidity. This is because the electron-donating group increases the electron density on the electron-deficient species. Thus, it makes it difficult to release ${{\text{H}}^{\text{ + }}}$ ions as the bonds are stronger. The presence of electron-withdrawing groups ${\text{ - N}}{{\text{O}}_{\text{2}}}$ decreases the electron density and facilitates the release of ${{\text{H}}^{\text{ + }}}$ ions. Other examples of electron-donating groups are ${\text{ - N}}{{\text{H}}_{\text{2}}}$, -NR, - etc., and the electron-withdrawing groups are halogen, ${\text{ - N}}{{\text{O}}_{\text{2}}}$, ${\text{ - C}}{{\text{F}}_{\text{3}}}$
Complete step by step answer:
Let us look at the structure of p-nitrophenol. Phenol is an electron-deficient group.
This is the lewis dot structure of ${\text{N}}{{\text{O}}_{\text{2}}}$.
We can see that Nitrogen in ${\text{N}}{{\text{O}}_{\text{2}}}$ already has a positive charge on it. It is because it gave one of its lone pairs to oxygen (double bond). When this nitrogen is attached to the benzene ring, the nitrogen will pull the electrons from the benzene ring to reduce the positive charge.
Therefore, ${\text{N}}{{\text{O}}_{\text{2}}}$ is an electron-withdrawing group.
In p-nitrophenol, since it is ${\text{N}}{{\text{O}}_{\text{2}}}$ is an electron-withdrawing group, all the electron density will be drifted towards ${\text{N}}{{\text{O}}_{\text{2}}}$
This will result in a decrease in the electron density of oxygen in the O-H bond.
Thus, the release of ${{\text{H}}^{\text{ + }}}$ is easier.
Now, let us look at o-cresol.
The ${\text{ - C}}{{\text{H}}_{\text{3}}}$ is attached to the para position of phenol.
We know that the methyl group in cresol is electron-donating. It gives its electron density to the electron-deficient phenol. Thus, the electron density on the O-H group increases.
Therefore, it cannot give out ${{\text{H}}^{\text{ + }}}$ ions.
Therefore, the correct answer is that the ${\text{ - N}}{{\text{O}}_{\text{2}}}$ decreases the electron density on the oxygen of the O-H group making p-nitrophenol a stronger acid.
Thus, the correct option is (B).
Note: The presence of an electron-donating group will decrease the acidity. This is because the electron-donating group increases the electron density on the electron-deficient species. Thus, it makes it difficult to release ${{\text{H}}^{\text{ + }}}$ ions as the bonds are stronger. The presence of electron-withdrawing groups ${\text{ - N}}{{\text{O}}_{\text{2}}}$ decreases the electron density and facilitates the release of ${{\text{H}}^{\text{ + }}}$ ions. Other examples of electron-donating groups are ${\text{ - N}}{{\text{H}}_{\text{2}}}$, -NR, - etc., and the electron-withdrawing groups are halogen, ${\text{ - N}}{{\text{O}}_{\text{2}}}$, ${\text{ - C}}{{\text{F}}_{\text{3}}}$
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
How do you arrange NH4 + BF3 H2O C2H2 in increasing class 11 chemistry CBSE
Is H mCT and q mCT the same thing If so which is more class 11 chemistry CBSE
Trending doubts
Difference Between Plant Cell and Animal Cell
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
How do you solve x2 11x + 28 0 using the quadratic class 10 maths CBSE
Select the correct plural noun from the given singular class 10 english CBSE
What organs are located on the left side of your body class 11 biology CBSE
The sum of three consecutive multiples of 11 is 363 class 7 maths CBSE
What is the z value for a 90 95 and 99 percent confidence class 11 maths CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
How many squares are there in a chess board A 1296 class 11 maths CBSE