Chapter 8, Problem 30P

(a)

Interpretation Introduction

Interpretation:Compound ${\text{CH}}_3{\text{CHClCH}}_2\text{OH}$ , ${\text{CH}}_3{\text{CHBrCH}}_2\text{OH}$ and ${\text{BrCH}}_3{\text{CH}}_2{\text{CH}}_2\text{OH}$ should be ranked in order of decreasing acidity.

Concept introduction:In accordance with Bronsted definition an acid can act as a proton donor and a base can act as a proton acceptor. Thus in a typical acid-base reaction, the fundamental principle is a lone pair of base reaches out for an acidic proton. Similar curved arrows are used to show the movement of electrons. After deprotonation, the species left with a negative charge is referred as the conjugate base of acid while the other with a positive charge is termed conjugate acid of given base. For example;

  

The strength of various conjugate acid-base pairs varies inversely to one another; the strong acid has a weak conjugate base and the strong base has weak conjugate acid and vice-versa.

The order of acidic strength of various alcohols is as follows:

  ${\text{CH}}_{\text{3}}\text{OH}<1°<2°<3°$

For tertiary alcohols, the steric bulk is maximum that leads to inhibition in solvation of $\text{tert-butoxide}$ ion. This in turn raises the ${\text{pK}}_{\text{a}}$ of corresponding tertiary alcohol and thus reduces their acidity. On the other hand methanol has lowest ${\text{pK}}_{\text{a}}$ of theses alcohols. It can readily solvated by solvent and thus is most acidic.

(b)

Interpretation Introduction

Interpretation:Compounds ${\text{CH}}_3{\text{CCl}}_2{\text{CH}}_2\text{OH}$ , ${\text{CCl}}_3{\text{CH}}_2\text{OH}$ and ${\left({\text{CH}}_3\right)}_2{\text{CClCH}}_2\text{OH}$ should be ranked in order of decreasing acidity.

Concept introduction: In accordance with Bronsted definition an acid can act as a proton donor and a base can act as a proton acceptor. Thus in a typical acid-base reaction, the fundamental principle is a lone pair of base reaches out for an acidic proton. Similar curved arrows are used to show the movement of electrons. After deprotonation, the species left with a negative charge is referred as the conjugate base of acid while the other with a positive charge is termed conjugate acid of given base. For example;

  

The strength of various conjugate acid-base pairs varies inversely to one another; the strong acid has a weak conjugate base and the strong base has weak conjugate acid and vice-versa.

The order of acidic strength of various alcohols is as follows:

  ${\text{CH}}_{\text{3}}\text{OH}<1°<2°<3°$

For tertiary alcohols, the steric bulk is maximum that leads to inhibition in solvation of $\text{tert-butoxide}$ ion. This in turn raises the ${\text{pK}}_{\text{a}}$ of corresponding tertiary alcohol and thus reduces their acidity. On the other hand methanol has lowest ${\text{pK}}_{\text{a}}$ of theses alcohols. It can readily solvated by solvent and thus is most acidic.

(c)

Interpretation Introduction

Interpretation:Compounds ${\left({\text{CH}}_3\right)}_2{\text{CH}}_2\text{OH}$ , ${\left({\text{CF}}_3\right)}_2{\text{CH}}_2\text{OH}$ and ${\left({\text{CCl}}_3\right)}_2{\text{CH}}_2\text{OH}$ should be ranked in order of decreasing acidity.

Concept introduction: In accordance with Bronsted definition an acid can act as a proton donor and a base can act as a proton acceptor. Thus in a typical acid-base reaction, the fundamental principle is a lone pair of base reaches out for an acidic proton. Similar curved arrows are used to show the movement of electrons. After deprotonation, the species left with a negative charge is referred as the conjugate base of acid while the other with a positive charge is termed conjugate acid of given base. For example;

  

The strength of various conjugate acid-base pairs varies inversely to one another; the strong acid has a weak conjugate base and the strong base has weak conjugate acid and vice-versa.

The order of acidic strength of various alcohols is as follows:

  ${\text{CH}}_{\text{3}}\text{OH}<1°<2°<3°$

For tertiary alcohols, the steric bulk is maximum that leads to inhibition in solvation of $\text{tert-butoxide}$ ion. This in turn raises the ${\text{pK}}_{\text{a}}$ of corresponding tertiary alcohol and thus reduces their acidity. On the other hand methanol has lowest ${\text{pK}}_{\text{a}}$ of theses alcohols. It can readily solvated by solvent and thus is most acidic.