Chapter 27 Flashcards
What are amines?
Organic compounds derived from ammonia, NH₃, in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring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 the formula of ammonia?
NH₃
What is an aliphatic amine?
Nitrogen attached to at least one straight/branched carbon chain (alkyl group, R)
What is the simplest aliphatic amine?
Methylamine, CH₃NH₂
What is an aromatic amine?
Nitrogen atom attached to aromatic ring (aryl group)
What is the simplest aromatic amine?
phenylamine, C₆H₅NH₂
What are amines classified as?
1) primary
2) secondary
3) tertiary
How are amines classified?
By the number of alkyl or aryl groups attached to the nitrogen atom
What are amines well known for?
Their effects on the body
How do you name a primary amine, with the -NH₂ group on the end of the chain?
Add -amine to the name of the alkyl chain
How do you name a primary amine, with the -NH₂ group on any other carbon but carbon-1?
Use the prefix amino- and add a number before to indicate the position of the amine group along the chain
How do you name a secondary/tertiary amine containing the same alkyl group?
1) use the prefixes di- or tri- to indicate the number of alkyl groups attached to the nitrogen atom
2) use the suffix-amine
When two or more different groups are attached to a nitrogen atom, what is the compound named as?
N-substituted derivative of the larger group
What is the name of CH₃NHCH₂CH₂CH₃?
N-methylprophlamine
What is the name of CH₃N(CH₂CH₃)CH₂CH₂CH₃?
N-ethyl-N-methylpropylamine
Why do amines behave as bases?
The lone pair of electrons on the nitrogen atom can accept a proton
When amine accepts a proton, what type of bond is formed between the lone pair of electrons on the nitrogen atom and the proton?
Dative covalent bond
ethylamine + proton —>
ethylammonium ion
What should you show when drawing the structure of amine?
lone pair
Are amines acids or bases?
bases
What do amines neutralise acids to make?
salts
CH₃CH₂CH₂NH₂ + HCl —>
CH₃CH₂CH₂NH₃⁺Cl⁻
2CH₃CH₂NH₂ + H₂SO₄ —>
(CH₃CH₂NH₃⁺)₂SO₄²⁻
Is ammonia an electrophile or nucleophile?
nucleophile
How do you form a primary amine?
1) ammonia + haloalkane —> ammonium salt
2) ammonium salt + aqueous alkali —> amine + salt + water
Why can ammonia act as a nucleophile in a substitution reaction with a haloalkane?
Ammonia has a lone pair of electrons on the nitrogen atom
What type of reaction is ammonia + haloalkane?
substitution reaction
1-chloropropane + ammonia —>
propylammonium chloride
CH₃CH₂CH₂Cl⁺NH₃ —>
CH₃CH₂CH₂NH₃⁺Cl⁻
propylammonium chloride + sodium hydroxide —>
propylamine + sodium chloride + water
CH₃CH₂CH₂NH₃⁺Cl⁻ + NaOH —>
CH₃CH₂CH₂NH₂ + NaCl + H₂O
What are the essential conditions when forming primary amines?
1) ethanol is used as the solvent
2) excess ammonia is used
Why is ethanol used as the solvent when forming primary amines?
Prevents any substitution of the haloalkane by water to produce alcohols
Why is excess ammonia used when forming primary amines?
Reduces further substitution of the amine group to form secondary and tertiary amines
Why is the reaction used for making primary amines not suitable 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
primary amine + haloalkane —>
ammonium salt
CH₃CH₂CH₂Cl + CH₃CH₂CH₂NH₂ —>
(CH₃CH₂CH₂)₂NH⁺Cl⁻
How do you obtain a secondary amine from its salt?
By reacting the salt with sodium hydroxide
(CH₃CH₂CH₂)₂NH₃⁺Cl⁻ + NaOH —>
(CH₃CH₂CH₂)₂NH + NaCl +H₂O
How do you form tertiary amines?
Further reaction of the secondary amine
How do you form a secondary amine?
Further reaction of the primary amine
How is phenylamine made?
By reducing nitrobenzene
1) nitrobenzene heated under reflux with tin + hydrochloric acid —> ammonium salt
2) ammonium salt reacted with excess sodium hydroxide —> aromatic amine + water
What is an amino acid?
Organic compound containing both amine, NH₂, and carboxylic acid, COOH, functional groups
How many common amino acids does the body have?
20
What is an α-amino acid?
The amine group is attached to the α-carbon atom - the second carbon atom, next to the carboxyl group
How do the 20 amino acids differ?
By the side chain, R, attached to the same alpha-carbon atom
What is the general formula of an alpha-amino acid?
RCH(NH₂)COOH
What is the β-carbon atom?
third carbon
What is the γ-carbon atom?
fourth carbon
What do amino acid react with acids to form?
salts
What do carboxylic acids react with alkalis to form?
salts
What do carboxylic acids react with alkalis to form?
esters
What do amino acids react with alkalis to form?
salt + water
What aqueous alkalis do amino acids react with?
1) sodium hydroxide
2) potassium hydroxide
How are amino acids esterified?
By heating with an alcohol in the presence of concentrated sulfuric acid
What is a zwitterion?
Amine group that accepts a proton from the carboxylic acid group to form an ion containing both a positive and negative charge
What is the overall charge of a zwitterion?
Zwitterions have no overall charge
Why do zwitterions have no overall charge?
The positive and negative charges cancel out
What is the isoelectric point?
The pH at which the zwitterion is formed
If an amino acid is added to a solution with a pH greater than its isoelectric point, what happens?
The amino acid behaves as an acid and loses a proton
If an amino acid is added to a solution with a pH lower than its isoelectric point, what happens?
The amino acid behaves as a base and gains a proton
What are amides?
The products of reactions of acyl chlorides with ammonia and amines
Where are amide groups common?
In nature
What are amides classified as?
1) primary
2) secondary
3) tertiary
What is a primary amine?
One carbon atom bonded to N
What is a secondary amine?
Two carbon atoms bonded to N
What is a tertiary amine?
Three carbon atoms bonded to N
What are stereoisomers?
Compounds with the same structural formula but a different arrangement of atoms
Where is optical isomerism found?
In molecules that contain a chiral centre
What is the chiral centre?
A carbon atom that is attached to four different atoms or groups
What does the presence of a chiral carbon atom mean?
The existence of two non-superimposable mirror image structures
What are optical isomers/enantiomers?
two non-superimposable mirror image structures
For each chiral carbon atom, how many pairs of optical isomers are there?
One
How is a chiral carbon shown?
Labelled with an asterisk
How are optical isomers drawn?
To show the 3D tetrahedral arrangement of 4 different groups around central chiral carbon atom
How do alkenes form polymers?
Addition polymerisation
What are the two important condensation polymers?
1) polyesters
2) polyamides
What is condensation polymerisation?
The joining of monomers with loss of a small molecule, usually water/hydrogen chloride
What can polyesters be made from?
1) 1 monomer - containing both carboxylic acid and alcohol groups
2) 2 monomers - 1 contaning 2 carboxylic acid groups, 1 containing 2 alcohol groups
What are the monomers for the polyester formation where 2 monomers are involved?
1) diol
2) dicarboxylic acid
What other acid can a polyester be made using?
diacyl chloride
When a diacyl chloride is used to make a polyester, what is lost, instead of water?
hydrogen chloride
What are polyamides
Condensation polymers formed when monomers are joined together by amide linkages in a long chain to form the polymer
What can polyamides be made from?
1) 1 monomer - containing both carboxylic acid (or acyl chloride) and amine groups
2) 2 monomers - 1 containing 2 carboxylic acid (or acyl chloride) groups, 1 containing 2 amine groups
What do amino acids undergo condensation polymerisation to form?
polypeptides/proteins
What does a polypeptide/protein contain?
Many different amino acids all linked together by amide bonds
What can polyesters + polyamides be hydrolysed using?
1) hot aqueous alkali (sodium hydroxide)
2) hot aqueous acid (hydrochloric acid)
What shape are amines?
trigonal pyramidal
What is the bond angle of amines?
107°
What intermolecular forces do amines have?
1) hydrogen bonding
2) the N-H bond is polar
3) lone pair of electrons on the Nitrogen atom
Are the intermolecular forces in amines stronger or weaker than alcohols?
Weaker because Nitrogen has a lower electronegativity value than Oxygen, which means the hydrogen bonding is weaker
In order to be the strongest base, what must an amine have?
A greater electron density around the Nitrogen atom to make it a better electron pair donor
What conditions are needed to form nitrobenzene from benzene?
1) concentrated sulfuric acid
2) nitric acid
What is the equation for the production of phenylamine, C₆H₅NH₂ from nitrobenzene, C₆H₅NO₂?
C₆H₅NO₂ + 6[H] –> C₆H₅NH₂ + 2H₂O
What is [H]?
reducing agent
