Nitriles, Amines and Amides Flashcards
What are amines
- Amines are organic compounds derived from ammonia, NH3, in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring
What is an aliphatic amine
- In an aliphatic amine the nitrogen atom is attached to at least one straight or branched carbon chain (alkyl group).
- Methylamine is the simplest aliphatic amine CH3NH2
What is an aromatic amine
- In an aromatic amine the nitrogen atom is attached to an aromatic ring
- Phenylamine is the simplest aromatic amine C6H5NH2
What is the difference between primary, secondary and tertiary amines and give examples
- Primary- 1 alkyl/aryl group attached to the nitrogen
e. g. CH3CH2CH2NH2, C6H5NH2 - Secondary- 2 alkyl/aryl groups attached to the nitrogen
e. g. (C2H5)2NH, C6H5NH(CH3) - Tertiary- 3 alkyl/aryl groups attached to the nitrogen
e. g. (CH3)3N, C6H5N(CH3)2
How do you name amines
- Primary amine with NH2 on the end of the chain- Add the suffix amine to the name of the alkyl chain e.g ethylamine
- Primary amine with NH2 on any other carbon except C-1 - Use prefix amino and a number in front to indicate its position on the carbon chain e.g 2-aminobutane
- Secondary/tertiary amines that contain the same alkyl group- prefix di or tri are used to indicate number of alkyl groups attached e.g (CH3)2NH is dimethylamine
- When two or more different groups are attached to a nitrogen atom- the compound is named as a N-substituted derivative of a larger group. e.g CH3NHCH2CH2CH3 is N-methylpropylamine
- Practice naming p6 of study pack
Name the following compounds:
- NH2CH2CH2CH2CH2NH2
- CH3CH2CH(NH2)CH2CH2CH3
- 1,4-diaminobutane
2. Hexyl-3-amine
How do amines behave in their chemical reactions and give an example with ethlyamine
- Behave as bases
- As the lone pair of electrons on the nitrogen atom can accept a proton
- When an amine accepts a proton, a dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton
- C2H5HN2 + H+ → [C2H5NH3]+
ethylamine + proton→ ethylammonium ion
What is formed when amines react with acids and give 2 examples:
- Propylamine + HCl
- Ethylamine + H2SO4
- They neutralise acids to make salts as they are bases
- CH3CH2CH2NH2 + HCl → CH3CH2CH2NH3+Cl-
propylamine + HCl → propylammonium chloride - 2CH3CH2NH2 + H2SO4 → (CH3CH2NH3+)2SO4 2-
ethylamine + H2SO4 → ethylammonium sulfate
Describe and explain the difference of boiling point of 1-aminobutane compared to pentane and butan-1-ol
- 1-aminobutane has hydrogen bonds between molecules which are stronger than London forces in pentane
- However, the hydrogen bonds are weaker than those in butan-1-ol
Describe the formation of primary amines and show an example with 1-chloropropane
- Ammonia has a lone pair of electrons o the nitrogen atom which allows ammonia to act as a nucleophile in a substitution reaction with a haloalkane. Forming an ammonium salt
CH3CH2CH2Cl + NH3 → CH3CH2CH2NH3+Cl-
1-chloropropane + NH3 → propylammonium chloride (salt) - Aqueous alkali is then added to generate the amine from the salt.
CH3CH2CH2NH3+Cl- + NaOH → CH3CH2CH2NH2 + NaCl + H2O
propylammonium chloride + NaOH → propylamine
What are the conditions needed for the formation of primary amines
- Ethanol is used as the solvent- this prevents any substitution of the haloalkane by water to produce alcohols. And haloalkanes aren’t soluble in water.
- Excess ammonia is used- this reduces further substitution of the amine group to form secondary and tertiary amines
Describe the formation of secondary and tertiary amines and five an example with propylamine and 1-chloropropane
- The reaction to make primary amines is unsuitable for making a pure primary amine.
- The product still contains a lone pair of electrons on the nitrogen atom that can react further with a haloalkane to form a secondary amine- the product is an ammonium salt.
CH3CH2CH2Cl + CH3CH2CH2NH2 → (CH3CH2CH2)2NH2+Cl-
1-chloropropane + propylamine → dipropylammonium chloride - The secondary amine is obtained from the salt by reacting with NaOH
(CH3CH2CH2)2NH2+Cl- + NaOH → (CH3CH2CH2)2NH + NaCl + H2O
dipropylammonium chloride → dipropylamine - Tertiary amines can also be formed by further reaction of the secondary amine e.g form tripropylamine
Describe the preparation of aromatic amines and give an example using phenylamine
- Phenylamine is made by the reduction of nitrobenzene
- Nitrobenzene is heated under reflux with tin and HCl to form the ammonium salt phenylammonium chloride
- This is then reacted with excess NaOH to produce the aromatic amine
- The tin and HCl act as reducing agent.
- Nitrobenzene + 6[H] → phenylamine + 2H2O
- Sn/conc Hcl and excess NaOH (aq) are written above and below the arrow
Which functional groups are present in all amino acids
- Carboxylic acid
2. Amine
Describe and draw the basic structure of an α-amino acid
- Amine group is attached to the α-carbon atom- the second carbon next to the carborxylic acid group
- They differ by side chain R
- General formula- RCH(NH2)COOH
Describe the reactions of the amine group in an amino acid and show an example with 2-aminopropanoic acid and HCl
- The amine group is basic and reacts with acids to make salts. So amino acids will also react with acids to form salts
- CH3CH(NH2)COOH + HCl → CH3CH(NH3+)COOH + Cl-
What are the two main reactions of the carboxylic acid group in amino acids
- React with alkalis to form salts
2. React with alcohols to form esters
Describe the reactions of the carboxylic acid group in amino acids and aqueous alkalis and give example with aminoethanoic acid
- An amino acid reacts with an aqueous alkali e.g Na/KOH to form a salt and water
- CH2(NH2)COOH + NaOH → CH2(NH2)COO-Na+ + H2O
Describe the reactions of the carboxylic acid group in amino acids and alcohols and give example with aminoethanoic acid
- Amino acids are easily esterified by heating with an alcohol in the presence of concentrated sulfuric acid
- CH2OHCH(NH2)COOH + C2H5OH + H+ → CH2OHCH(NH3+)COOC2H5 + H2O
- The acidic conditions protonate the basic amine group of the ester.
What are amides
- Amides are the products of reactions of acyl chlorides with ammonia and amines
- There are primary, secondary and tertiary amides
- It consists of a carbonyl group bonded to a nitrogen
- Primary if the nitrogen is attached to one carbon
- Secondary if nitrogen is attached to two carbons etc.
Describe the reaction between acyl chlorides and ammonia and give example with ethanoyl chloride
- Ammonia can act as a nucleophile by donating the lone pair of electrons on the nitrogen atom to an electron-deficient species
- Forms primary amides when reacting with acyl chlorides (Nitrogen atom attached to one carbon atom)
- CH3COCl + 2NH3 → CH3CONH2 + NH4Cl
Describe the reaction between acyl chlorides and amines and give an example with ethanoyl chloride and methylamine
- Primary amine reacts with acyl chloride in the same way as ammonia to form secondary amide (Nitrogen atom attached to two carbon atoms)
- CH3COCl + 2CH3NH2 → CH3CONHCH3 + CH3NH3+Cl-
Write an equation for the reaction of ethanoyl chloride with ammonia
CH3COCl + NH3 →CH3CONH2 + HCl
Define stereoisomers
Compounds with the same structural formula but with a different arrangement of the atoms in space
Define optical isomers
Stereoisomers that are non-superimposable mirror images of each other; also called enantiomers
Name the two main types of isomerism and give examples of each
- Structural isomerism- different structural formula
- chain isomerism
- positional isomerism
- functional group isomerism - Stereoisomerism
- E/Z isomerism
- optical isomerism
Describe where optical isomerism is found
- Optical isomerism is found in molecules that contain a chiral centre (carbon atom that is attached to four different atoms of groups of atoms)- doesn’t have to be carbon but in organic chemistry it normally is
- The presence of a chiral carbon atom in a molecule leads to the existence of two non-superimposable mirror image structures
- For each chiral carbon there is always one pair of optical isomers
Describe how you get optical isomers in amino acids
- Except for glycine- H2NCH2COOH, all α-amino acids contain a chiral carbon atom
- The α-carbon atom is bonded to four different atoms or groups
How do you draw an optical isomer
- They are drawn to show 3D tetrahedral arrangement of the four different groups around the central chiral carbon atom.
- Once one isomer has been drawn, the other isomer is drawn as a mirror image, reflecting the first structure.
- A dotted line between the two isomers is often drawn to represent a mirror
Give two examples of condensation polymers
- Polyesters
2. Polyamides
Describe the different combinations of monomers that can form polyamides
- One monomer containing both a carboxylic acid and an amine group
- Two monomers- one containing two carboxylic groups and one containing two amine groups
Describe the formation of polyamides from one monomer containing two functional groups
- Amino acids contain carboxylic acid group and an amine group
- They can undergo condensation polymerisation of form polypeptides or proteins
- Water is lost in this reactions when an amide bond is formed
- The bond forms between COOH group and NH2 group, the OH and H break off to form water.
Describe the formation of polyamides from two monomers each with two functional groups
- Reaction of dicarboxylic acid with diamine
- An amide bond forms between the amine on one monomer and the carboxyl group on the other monomer.
- Water is formed
State the two ways that a polyamide can be hydrolysed
Reflux with either:
- Using hot aqueous alkali (NaOH)
- Hot aqueous acid (HCl)
What are the products of the acid hydrolysis of a polyamide
- Carboxylic acid
2. Amine salt
What are the products of the alkaline hydrolysis of a polyamide
- Carboxylate salt
2. Amine
