Chapter 27 - amides, amino acid and polymers 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Amines are organic compounds, derived from ammonia, NH3, in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring.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?
a. In an aliphatic amine, the nitrogen atom is attached to at least one straight or branched carbon chain (alkyl group, R).
b. Methyl amine, CH3NH2, is the simplest aliphatic amine with one methyl group attached to the nitrogen atom.
What is an aromatic amine?
a. In an aromatic amine, the nitrogen atom is attached to an aromatic ring (aryl group, Ar).
b. Phenylamine is the simplest aromatic amine, with a phenyl group attached to the nitrogen atom.
What are amines well known for?
a. Serotonin acts as a neurotransmitter.
b. Pseudoephedrine – an active ingredient in decongestion medications.
How do amines act as bases?
a. The lone pair of electrons on the nitrogen atom can accept a proton.
b. 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. For example, ethylamine accepts a proton and becomes [ethylammonium ion]+.
c. Amines are bases and they neutralise acids to make salts. For example, propylamine reacts with HCl to form the salt propylammonium chloride.
d. Ethylamine reacts with sulfuric acid to form ethylammonium sulfate.
How can you form primary amines?
a. NH3, has a lone pair of electrons on the nitrogen atom which allows ammonia to act as a nucleophile in a substitution reaction with a haloalkane.
b. The product of this reaction is an ammonium salt.
c. Aqueous alkali is then added to generate the amine from the salt.
How can you prepare propylamine?
a. React 1-chloropropane with ammonia. This produces propylammonium chloride (salt).
b. Now react the salt (propylammonium chloride) with sodium hydroxide to produce propylamine, NaCl, and H20.
c. The conditions of this reaction include, ethanol is used as a solvent. This prevents any substitution of the haloalkane by water to produce alcohols.
d. Excess ammonia is also used. This reduces further substitution of the amine group to form secondary and tertiary amines.
How can you prepare secondary and tertiary amines?
a. The reaction for producing a primary amine is unsuitable for making a pure primary amine.
b. The nitrogen on the primary amine contains a lone pair of electrons, which can further react with a haloalkane to form a secondary amine.
c. Therefore, react the primary amine with another haloalkane.
d. This produces a salt.
e. Now react the salt with NaOH, to form the di substituted amine with NaCl and H20 as the by-products.
f. Tertiary amines are produced by further reaction of secondary amine.
How are aromatic amines prepared, in particular, phenylamine?
a. Phenylamine, is made by the reduction of nitrobenzene.
b. Nitrobenzene is heated under reflux with tin and hcl to form the ammonium salt, phenylammonium chloride, which is then reacted with excess NaOH to produce the aromatic amine, phenylamine.
c. Tin and hydrochloric acid acts as a reducing agent, 6 moles of [H] are needed and 2 moles of water are produced.
d. Therefore, conditions for this reaction are, Sn/conc HCl and excess NaOH.
What are amides?
a. Amides are the products of the reactions of acyl chlorides with ammonia and amines.
b. It has the amide group (RC=0NR’R”).
How many optical isomers does a compound have?
a. For each chiral carbon atom, there is always one pair of optical isomers.
b. Therefore, there are 2^c number of optical isomers where c is the number of chiral centres.
What is chiral centre?
a. In organic chemistry, the chiral centre is a carbon atom that is attached to four different atoms or groups of atoms.
b. Chirality is not just reserved for carbon atoms and the term applies to any centre that holds four different attachments that can be arranged as two non-superimposable mirror image forms.
What is condensation polymerisation?
a. Condensation polymerisation is the joining of monomers with the loss of a small molecule, usually water (the condensation) or hydrogen chloride.
b. In condensation polymerisation, two different functional groups are needed.
What are the different types of condensation polymerisation?
a. Polyesters
b. Polyamides
How can you make a polyester?
a. Polyesters can be formed from one monomer containing both a carboxylic acid and an alcohol functional group.
b. From two monomers – one containing two carboxylic acid groups and the other containing two alcohol groups.
