Chapter 15, Problem 3MCP

(a)

Interpretation Introduction

Interpretation:

The statement “$\text{N-methylpropanamide}$ is a base” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is false because amides shows a presence of strong electronegative oxygen atom of carboxyl group causes a very strong attraction between the lone pair of nitrogen electrons and the carbonyl group.  Because, of which the unshared pair of electrons cannot hold a proton.

Explanation of Solution

Amide shows a presence of strong electronegative oxygen atom of carboxyl group causes a very strong attraction between the lone pair of nitrogen electrons and the carbonyl group.  Because, of which the unshared pair of electrons cannot hold a proton.

Hence, $\text{N-methylpropanamide}$ is a not base and the given statement is false.

(b)

Interpretation Introduction

Interpretation:

The statement “$\text{N-methylpropanamide}$ has a higher melting point than $\text{1-pentanamine}$” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

$\text{N-}$ methylpropanamide is an amide and $\text{1-}$ pentanamine is a primary amine.

Amides have highest melting point when compared to alcohols and amines.  This is because the amides appear to be most polar in nature because it can form both hydrogen bond and accept hydrogen bonds on both the oxygen atom and nitrogen atom.  Thus, they tend to form stronger intermolecular forces resulting in a higher boiling point.

The ability of primary and secondary amines to form $\text{N-H---N}$ hydrogen bond is reflected in their boiling points.  Because the nitrogen atom is less electronegative than the oxygen atom, the $\text{N-H}$ bond is less polar than the $\text{O-H}$ bond, for this reason, amines have lower melting points than alcohols and amides of comparable molar mass.

Hence, $\text{N-}$ methylpropanamide has higher melting point than $\text{1-}$ pentanamine and the given statement is true.

(c)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide forms hydrogen bonds with water” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

$\text{N-}$ methylpropanamide can form hydrogen bonds with water.  The hydrogen bonds are formed through their oxygen atoms to the hydrogen atoms of water and the $\text{N-H}$ hydrogen atoms can donate hydrogen bonds.  Thus, they form hydrogen bonds with water and the given statement is true.

(d)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide is nonpolar” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is false because $\text{N-}$ methylpropanamide is polar.

Explanation of Solution

The structure of $\text{N-}$ methylpropanamide is,

The carbonyl group present in $\text{N-}$ methylpropanamide is polar in nature and thereby can participate in dipole-dipole attractions.  Therefore, $\text{N-}$ methylpropanamide is polar in nature.

The statement “$\text{N-}$ methylpropanamide is nonpolar” is false due to the presence of polar carbonyl group in them; $\text{N-}$ methylpropanamide is polar in nature.

(e)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide has a molecular formula of ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}\text{NO}$” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

The structure of $\text{N-}$ methylpropanamide is,

From the structure of $\text{N-}$ methylpropanamide, it can be seen that it comprises of four carbon atoms, nine hydrogen atoms, and one nitrogen atom one oxygen atom.  The molecular formula of $\text{N-}$ methylpropanamide is ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}\text{NO}\text{.}$

Hence, the given statement is true.

(f)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide has a higher boiling point than pentanal” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

$\text{N-}$ methylpropanamide is an amide and pentanal is an aldehyde.

Amides have highest melting point when compared to aldehydes.  This is because the amides appear to be most polar in nature because it can form both hydrogen bond and accept hydrogen bonds on both the oxygen atom and nitrogen atom.  Thus, they tend to form stronger intermolecular forces resulting in a higher boiling point.  Because of the strong intermolecular forces in amides, $\text{N-}$ methylpropanamide has higher boiling point than pentanal.

Hence, the given statement is true.

(g)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide is a liquid at room temperature” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

$\text{N-}$ methylpropanamide is clear colorless and odorless liquid.  Hence, the statement “$\text{N-}$ methylpropanamide is a liquid at room temperature” is true.

(h)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide is water soluble” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

$\text{N-}$ methylpropanamide can form hydrogen bonds with water.  The hydrogen bonds are formed through their oxygen atoms to the hydrogen atoms of water and the $\text{N-H}$ hydrogen atoms can donate hydrogen bonds.  Thus, they are soluble in water and the given statement is true.

(i)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide has a carboxyl functional group” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is false because it comprises of carbonyl functional group.

Explanation of Solution

Carboxyl group consists of carbonyl group and hydroxyl group.

The structure of $\text{N-}$ methylpropanamide is,

$\text{N-}$ methylpropanamide shows the presence of carbonyl group and amide group.  Hence, the given statement is wrong.

(j)

Interpretation Introduction

Interpretation:

The statement “$\text{N-}$ methylpropanamide is a structural isomer of $\text{N-}$ ethylethanamide” has to be predicted as true or false.  If the statement is false, the reason for the false statement has to be described.

Answer to Problem 3MCP

The given statement is true.

Explanation of Solution

Structural isomers are those with same molecular formula but differ in arrangement of atoms.

The molecular formula of $\text{N-}$ methylpropanamide is ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}\text{NO}$ and its structure is,

The molecular formula of $\text{N-}$ ethylethanamide is ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}\text{NO}$ and its structure is,

Both these are structural isomers with each other and hence, the statement “$\text{N-}$ methylpropanamide is a structural isomer of $\text{N-}$ ethylethanamide” is true.