amines and amides

"What is the functional group of amines?"

Amines only contain the functional group NH2

"How can we prepare an amine?"

We can prepare an amine by heating excess ammonia with a halogenoalkane.

"How can we form an amide from an amine?"

We can react an amine with either an acyl chloride or acid anhydride to produce a amide

classifying amines

We classify amines according to the number of carbons bonded to nitrogen.

• 1 carbon bonded to nitrogen - primary amine 

• 2 carbons bonded to nitrogen - secondary amine 

• 3 carbons bonded to nitrogen - tertiary amine

To name amines where NH2 is at the end of the chain, we

1. Write the root (longest carbon chain)

2. add ‘yl’ to the root.

3. write the suffix ‘amine’.

When an amine group is attached to a benzene ring

Amine has higher priority than benzene so:

• We write the suffix amine

• Add the prefix phenyl

"How do we name secondary and tertiary amines in the exam?"

In the exam if you are asked to name secondary and tertiary amines they will normally have identical groups. Therefore we name secondary and tertiary amines in the same way we name primary amines but we add the multiple ‘di’ or ‘tri’ at the every front of the name depending on whether its primary or secondary

"How do we name secondary and tertiary amines with identical groups?"

To name secondary amines with identical groups, we add the multiplier ‘di’ .

To name tertiary amines with identical groups, we add the multiplier ‘tri’ .

Another example

To name primary amines where the amine group isn’t at the end of the chain, we

1. add ‘an’ to the root.

2. include a position number before the suffix.

3. write the suffix ‘amine’.

   

Naming more complicated primary alkenes

When our molecule contains lower priority functional groups we can just add them to our prefix as usual

For example:

This amine contains a methyl group on the 3rd carbon so it is called 3-methylbutan-2-amine

Positon number of functional group - functional group name - longest carbon chain - an (since NH2 isn't at the end of the chain) - position number of amine group - amine

"How do we name amines when they are the highest priority functional group?"

When the amine is the highest priority functional group, we write the suffix ‘amine'

In this example amines are higher priority than halogenoalkanes

"How do we name amines when they are not the highest priority functional group?"

When the amine isn’t the highest priority functional group, we write the prefix 'amino'

In this example alcohol is higehr prioirty.

So we write the positon number of the amine group- amino- longest carbon chain- positon of alcohol - ol suffix

"How do we classify amines as aliphatic or aromatic?"

We classify an amine as either aliphatic or aromatic according to whether a benzene ring is directly bonded to nitrogen.

"What makes an amine aromatic?"

Aromatic - if a benzene ring is directly bonded to nitrogen

"What makes an amine aliphatic?"

Allaphatic - if a benzene ring is not directly bonded to nitrogen

aromatic compounds

aliphatic compounds

We classify amides according to the number of carbons bonded to nitrogen .

1. In primary amides - 1 carbon bonded to nitrogen 

2. Secondary amides - 2 carbons bonded to nitrogen 

3. Tertiary amides - 3 carbons bonded to nitrogen

To name primary amides, we…

1. Use the longest carbon chain to write the root 

2. add ‘an’ to the root.

3. write the suffix ‘amide’.

"How do you name amides with substituents?"

If our amide has substituents we add them to the prefix the same as always.

Amides are the 2nd highest priority functional groups.

Position numver of substitutent - name of subsituent - name of longest cabron chain (in this case its 3 carbons) - ‘an’ ( add an to root) ---- add suffix amide

To name secondary amides, we...

treat the group without the carbonyl group as a substituent. The group with the cabronyl group as the main chain.

Therefore the substituent group (group without the carbonyl group) is in the prefix

We then write N- before the prefix.

To name tertiary amides with identical substituents, we

write ‘N,N-’ at the beginning of the name.

add the multiplier ‘di’.

To name tertiary amides with identical substituents, we

write ‘N,N-’ at the beginning of the name.

add the multiplier ‘di’.

To name tertiary amides with non-identical substituents, we

write ‘N-’ before each substituent.

write the substituents in alphabetical order.

primary, secondary and tertiary amines and amides

What type of bonds can amines and amides form with water?

All amines and amides can form hydrogen bonds with water.

How does the solubility of amines and amides in water change with increasing molecular size, and why?

The solubility of amines and amides in water decreases as the size of the molecule increases. Small amides and amides are highly soluble in water but larger molecules are less soluble. This is because a greater religion of the substance is nonpolar and non polar substances are insoluble in water

Why can amines act as both nucleophiles and bases?

Amines have a lone pair of electrons so they can act as a nucleophile and a base

Why do primary and secondary amines and amides have higher boiling points than tertiary amines?

Primary and secondary amines and amides have higher boiling points than tertiary amines because they experience hydrogen bonding between molecules

How can we measure the strength of bases?

We can measure the strength of bases by measuring their pH . The higher the pH , the stronger the base.

Which type of amines are the strongest bases, and which are the weakest?

In general the strongest bases are Aliphatic amines

The weakest bases are Aromatic amine

Arrange the following from strongest to weakest base: aliphatic amines, ammonia, aromatic amines.

Strongest to weakest: alphatic amines, ammonia, aromatic amines

How is the strength of a base determined in relation to the nitrogen atom?

Base strength is determined by how available the lone pair on nitrogen is.

What makes a nitrogen lone pair more available for proton acceptance?

The better the lone pair is at accepting a proton , the more available it is. And so the stronger the base.

Why are aliphatic amines stronger bases than ammonia?

In aliphatic amines, the alkyl groups donate electron density/electrons to nitrogen.

This means that the lone pair is better at accepting a proton . And so, we say that the lone pair is more available .

This also means that aliphatic amines are stronger bases than ammonia.

"How do we show electron movement in aliphatic amides?"

We can draw the direction the electrons move with an arrow on the carbon-nitrogen (C-N) bond.

How does delocalisation of the nitrogen lone pair in aromatic compounds affect its availability and base strength?

Why is phenylamine a weaker base than ammonia?

Phenylamine (aromatic compound) is a weaker base than ammonia because, in phenylamine, nitrogen's lone pair is delocalised (as it participates in the pi system). This means it is less likely to accept a proton. Therefore nitrogens lone pair is less available in aromatic compounds than amonias so it is a weaker base

"How do we show electron movement in aromatic amides?"

We can represent the direction the electron move in aromatic compounds like this. (arrow pointing away form nitrogen)

How does the number of alkyl groups bonded to nitrogen affect the strength of a base?

As the number of alkyl groups bonded to nitrogen increases, the strength of the base increases

Why do more alkyl groups increase base strength?

This is because more alkyl groups increase the amount of electron density donated to nitrogen. This makes the lone pair more available

How does the number of benzene rings directly bonded to nitrogen affect the strength of a base?

A

s the number of benzene rings directly bonded to nitrogen increases, the strength of the base decreases.

Why does an increase in benzene rings decrease base strength?

This is because nitrogens amine is delocalized across more pi systems (depending on number of rings). This makes the lone pair less available.

Exam How To: Strength of Amines

To answer these questions you get 5 marks for stating and explaining the effects of alkyl groups and benzene rings on amines base strength. To do this remember these five points

Finally you get 1 mark for writing a short sentence identifying the strongest and weakest base. 

To answer these questions you get 5 marks for stating and explaining the effects of alkyl groups and benzene rings on amines base strength. To do this remember these five points

"What happens when primary amines react with acyl chlorides?"

Primary amines react with acyl chlorides and act as a nucleophile. This is an addition elimination reaction

"What happens when primary amines react with acid anhydrides?"

Primary amines react with acid anhydrides and acts a nucleophile. This is an addition elimination reaction

"What happens when primary amines react with acyl chlorides?"

Primary amines react with acyl chlorides and act as a nucleophile. This is an addition elimination reaction

Primary amines react with acid anhydrides and acts a nucleophile. This is an addition elimination reaction

"Reaction of Primary Amines with Acid Anhydrides"

Primary amines react with acid anhydrides and acts a nucleophile. This is an addition elimination reaction what do i put on the front og my flashcarfd]

"Effect of Excess Halogenoalkane on Amine Reactions"

The chance of amines reacting with the halogenoalkane increases when we use excess halogenoalkane.

Why can ammonia, amines, and tertiary amines undergo nucleophilic substitution reactions with halogenoalkanes?

Ammonia, primary amines, secondary amines and eritary amines all have lone pairs of electrons which means they can undergo nuclepphilic substitution reaction with halogenoalkanes. The chance of these reactions occurring increase when we use excess halogenoakane.

Mechanism for nucleophilic substitutions

reactions with amines

"Quaternary Ammonium Ion Structure and Properties"

This is a quaternary ammonium ion. 4 carbon directly bonded to a N with a positive charge

"Quaternary Ammonium Salt Formation"

When quaternary ammonium ions form a complex with anions, we call the compound a quaternary ammonium salt

What are quaternary ammonium salts, and how are they used in everyday items?

In A level you need to know that Quaternary ammonium salts can be used as cationic surfactant. Surfactants are found in many everyday items like soap and shampoo. The above shows a structure of a cationic surfactant

Cationic Surfactants: Cationic Surfactants:

These have a positively charged hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. The positive charge comes from a quaternary ammonium group

How do surfactant clean

Step 1: The hydrophobic tail dissolves in the oil or grease, while the hydrophilic head remains in the water.

Step 2: The surfactant molecules arrange into micelles with the hydrophobic tails inward, trapping oil or grease inside.

Step 3: The hydrophilic heads face outward, allowing the micelles to be washed away with water, carrying the dirt or grease with them.

To prepare a primary amine from a halogenic alkane:

We react the halogenoalkane with 

• High pressure

• Heat

• Ecesss ammonia dissolved in ethanol 

How To prepare amines from nitriles. In the exam you need to know the reagents required for this reaction, the equation and the products 

Hydrogen and a nickel catalyst - reagents

The preparation of amines from nitriles is an example of a reduction reaction.

2 methods for preparing primary amines

It’s more efficient to prepare primary amines from nitriles than halogenoalkanes because…

.With nitriles the atom economy is 100% and there is no further reaction

With halogenoalkanes the atom economy is less than 100% and further reaction are possible (even if we do use excess ammonia)

How to prepare aromatic amines

reduce aromatic nitro compounds using CONCENTRATED Hydrochloric acid and tin

"Reduction of Aromatic Nitro Compounds to Aromatic Amines"

When we reduce aromatic nitro compounds with HCl and tin, we produce an aromatic amine and H2O/water

"Reduction of Aromatic Nitro Compounds to Aromatic Amines"

When we write equations for the reduction of aromatic nitro compounds, we represent the reducing agent with H (in square brackets)

So aromatic nitro compound + nH (sqaure brackets) -------------- aromatic amine + water

Balance the water and H out

What can aromatic amines be used for?

Aromatic amines can be used to manufacture dyes.