amines

Question 1

define an amine

Answer 1

compound derived from ammonia molecules and contains a nitrogen atom where H atoms can be replaced with an organic group e.g. alkyls

Question 2

how do amines act as a base?

Answer 2

• proton bonds to an amine via a dative covalent bond (both electrons in bond originate from the lone pair of electrons on a N atom which accepts the proton)
• strength of base depends on availability of the lone pair of electrons on N atom (higher electron density=more readily available electrons)
• electron density on nitrogen dependant on type of group attached to the nitrogen

Question 3

how do you produce an aliphatic amine?

Answer 3

add halogenoalkane with excess ammonia (2NH3 as the 2nd ammonia gives its lone pairs to hydrogen which breaks away from the salt)
-ammonia is a nucleophile attacking delta + C and then leaves an alkylammonium salt with a positive N+H3 bonded and Cl-
-ammonium halide salt produced
(could replace 2NH3 with 2 amines if trying to make secondary amines,teritary amines etc.)

Question 4

what is the downside of using halogenoalkane with excess ammonia?

Answer 4

• it produces primary amines but can also produce secondary,tertiary and even quarternary salts so is impure
• this is because the N atom on the primary amine still has a lone pair of electrons so can act as a nucleophile and still react with a halogenoalkane to form a secondary amine then repeat to form a tertiary salt and so on

Question 5

how do you make aromatic amines?

Answer 5

• reduce nitrocompounds e.g. nitrobenzene with conc. HCl and tin catalyst to form a salt (ends NH3+Cl-)
• then react salt with an alkali e.g. NaOH to produce an aromatic amine e.g. phenylamine
• reducing agent tends to be 6[H] and side product tends to be 2H2O

Question 6

what are aromatic amines used for?

Answer 6

to make dye stuff and pharmaceuticals

Question 7

Identify the inorganic nitrogen-containing compound formed by the mixture of hydrochloric acid and sodium nitrite.

Answer 7

HNO2

Question 8

what do dye structures usually contain?

Answer 8

diazonium ions which have N=N bond but if from nitrile its a triple bond and it joins the compounds together in a polypeptide

Question 9

Suggest why the mixture must be kept at a low temperature.

Answer 9

to prevent decomposition