Amines and Amides

how are amines prepared from halogenoalkanes?

nucleophilic substitution with ammonia

amine functional group?

R-NH2

conditions required for halogenoalkane + ammonia -> amine?

ethanolic, heat, high pressure, excess ammonia

how are amides formed from amines?

additional-elimination reaction by adding acid anhydride or acyl chloride

5 classifications of amines?

primary, secondary, tertiary, aliphatic, aromatic

primary amine?

1 carbon bonded to nitrogen

secondary amine?

2 carbons bonded to nitrogen

tertiary amine?

3 carbons bonded to nitrogen on amine group

aliphatic amine?

• doesn't contain a benzene ring

• benzene ring is present but not directly bonded to nitrogen

aromatic amine?

has a benzene ring directly bonded to nitrogen

suffix for simple amines?

-yl amine

how to name amines if the amine group isn't at the end?

• use longest carbon chain for root

• use longest carbon chain for root

• add -an after root

• use -amine

• position number

draw 3-methylbutan-2-amine

prefix used if amine group isn't the highest priority?

amino-

suffix used if amine group is the highest priority?

-amine

what multiplier is used when naming secondary amines if groups attached to the nitrogen are identical?

di, e.g. dimethylamine

what multiplier is used when naming tertiary amines if 3 groups attached to nitrogen are identical?

tri, e.g. trimethylamine

order of functional group priority?

1 carboxylic acid

2 amide

3 nitrile

4 aldehyde

5 ketone

6 alcohol

7 amine

8 alkene

9 benzene

10 halogenoalkane

11 alkane

draw phenylamine

practice naming on uplearn pls

amide functional group?

O=C-NH2

3 classifications for amides?

primary, secondary, tertiary

primary amide?

nitrogen is bonded to 1 carbon

secondary amide?

nitrogen bonded to 2 carbons

tertiary amide?

nitrogen bonded to 3 carbons

suffix for naming amides?

• amide, e.g. propanamide

how to name secondary amides?

• N- before prefix

• group with the carbonyl group = main chain

• group without = substituent

what does the 'N-' mean when naming secondary and tertiary amides?

acts as a position number, tells you that the substituent is bonded to the nitrogen

when naming tertiary amides, if 2 substituent are identical, what multiplier is used?

di, e.g. N,N-Dimethylpropanamide

how do we name tertiary amides if the 2 substituents aren't identical?

name both with N- in front, then add in alphabetical order, e.g. N-ethyl-N-methylpropanamide

what intermolecular forces to amines and amides have?

• van der waals

• primary and secondary experience hydrogen bonding

why don't tertiary amides experience hydrogen bonding?

they don't have an N-H bond

melting and boiling point properties for amines and amides?

primary and secondary have higher melting and boiling points than tertiary

why do primary and secondary amines/amides have higher melting and boiling points than tertiary?

primary and secondary have hydrogen bonding

solubility properties of amines and amides?

• all small amines and amides are highly soluble in water

• as size of molecule increases, solubility decreases

why does solubility of amines/amides decrease as the size of molecule increases?

a greater region of the molecule is non-polar, non-polar molecules are highly soluble in water

why can amines act as bases when forming a bond with water or nucleophilic when reacting with electrophiles?

• nitrogen has 5 electrons in outer shell, so when they form 3 covalent bonds, it still has a lone pair

base properties: what is gas sweetening?

natural gas contains harmful gases, amines convert CO2 gas and hydrogen sulfate gas into less harmful products by acting as a base

base properties: issues with CO2 and hydrogen sulfide in natural gas?

can corrode pipes, hydrogen sulfide causes instant death at high concentrations

How is base strength measured?

pH

Order aliphatic, ammonia and aromatic in base strength?

Aliphatic > ammonia > aromatic

What determines base strength?

• if lone pair more or less available

• more available = stronger base

• lone pair better at accepting a proton = more available = stronger base

Why are aliphatic amines stronger bases than ammonia?

Lone pair of electrons on N atom more AVAILABLE to accept protons

why are aliphatic amines' lone pairs more available?

alkyl groups donate electron density to nitrogen via inductive effect = nitrogen is better at accepting a proton = increases availability of the lone pair = stronger base

How do alkyl groups stabilize carbocations?

by donating electron density to the carbon via inductive effect

trend in number of alkyl groups and base strength?

as number of alkyl groups bonded to the nitrogen increases

Why are aromatic amines weak bases?

p orbital containing lone pair on nitrogen becomes apart of the pi system on benzene ring, so becomes delocalised = lone pair is less available = weaker

nucleophilic properties of amines?

• nucleophilic addition-elimination reaction with acyl chlorides/acid anhydrides to form primary amides

• primary, secondary, tertiary, NH3 all undergo nucleophilic substitution with halogenoalkanes

why can primary, secondary, tertiary amines and ammonia all undergo nucleophilic substitution with halogenoalkanes?

they all have a lone pair on the nitrogen

when reacting halogenoalkanes with NH3, why is excess ammonia used?

to decrease chances of the amine (nucleophile) reacting with the halogenoalkane

if the concentration of halogenoalkane is increased, what happens?

chances of halogenoalkane and amine reacting increases

primary amine + halogenoalkane -> ?

secondary amine via nucleophilic substitution

secondary amine + halogenoalkane -> ?

tertiary amine via nucleophilic substitution

tertiary amine + halogenoalkane -> ?

quaternary ammonium ion

what is a quaternary ammonium ion?

4 carbons are directly bonded to the nitrogen atom, giving it a positive charge (NH4+)

how are quaternary ammonium SALTS formed?

quaternary ammonium ions always have a positive charge, so can form lattices with anions, e.g. Cl-

use of quaternary ammonium salts?

Cationic Surfactants (fabric softeners)

structure of cationic surfactants?

polar end (NH4+) that's highly soluble in water,

non-polar chain high insoluble in water

how to surfactants act when dissolved in water?

they move to the surface, polar head in the water, non-polar poke out of the surface

2 ways primary aliphatic amines are produced?

1) halogenoalkane + ammonia -> primary aliphatic amine via nucleophilic substitution

2) reduction of nitriles

conditions for nucleophilic substitution of halogenoalkanes with ammonia? why?

• ethanolic, to ensure ammonia reacts with halogenoalkane and not water

• heated to increase rate, NH3 has a low boiling point, so high pressure is used to keep it dissolved in ethanol

• excess ammonia to prevent further reaction of primary amine to secondary

how are primary aliphatic amines produced from nitriles?

• nitriles in solution, metal catalyst added (Ni), bubble in H2

• H2 (g) is the reducing agent

in each reduction of nitrile reaction, how many hydrogens are added to the nitrile?

4, C-N triple bond breaks -> CH2-NH2 single bond

general equation for reduction of a nitrile?

RCN + 2H2 -> RCH2NH2

why are nitriles preferred to halogenoalkanes when producing primary aliphatic amines?

• efficient due to 100% atom economy (only 1 product produced, using halogenoalkane produces a salt too)

• no chance of any further reactions = 100% atom economy + efficient

why is using halogenoalkanes less efficient?

• atom economy isn't 100% as a salt is also produced

• although we use excess ammonia to decrease chance of amine + halogenoalkane it still happens, producing secondary and tertiary = decreases atom economy more

how are aromatic amines produced?

By reducing an aromatic nitro compound, like nitrobenzene,

nitro groups are reduced to NH2

what is an aromatic nitro compound?

aromatic compounds containing a nitro group (NO2)

conditions required for reduction of aromatic nitro compounds to produce aromatic amines?

concentrated HCl and Sn (tin) mixture

general equation for reduction of aromatic nitro compounds?

C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O

what does the [H] represent in the equation?

reducing agent

use of aromatic amines?

manufacturing dyes