19A.2

Question 1

as the hydrocarbon chain of primary aliphatic amines increases the solubility

Answer 1

decreases, with the first few amines in the homologous series increasing in solubility and being completely miscible (capable of mixing) with water (but when it gets proportionally larger chains the solubility decreases)

Question 2

why are the primary aliphatic amines dissolve in water

Answer 2

because the nitrogen can form hydrogen bonds with the water molecule (as well as the hydrogen with the oxygen of water)

Question 3

how is the solubility of phenylamine in water

Answer 3

only slightly soluble in water

Question 4

what can amines also do with water

Answer 4

they can slightly react with water to form an alkaline solution (CH3HN2 + H2O ⇌ CH3NH3^+1 + OH^-1

Question 5

why is the reaction between water and ammonia, and water and primary amine similar to each other

Answer 5

because they both have a nitrogen atom with lone pair of electrons that can form a dative bond with the hydrogen in the water molecule

Question 6

what is the reaction between ammonia and water

Answer 6

NH3 + H2O —–> NH4^+1 + OH^-1

Question 7

why does the solubility of the primary aliphatic amines decrease as the hydrocarbon increases

Answer 7

because the London forces between the carbon and the hydrogen will become more dominant and the polar bond between the nitrogen and hydrogen will become weaker making harder to make a hydrogen bond.

Question 8

what is the carbocation in the equation of water + amine

Answer 8

(Alkali)ammonium ion as in a alkali like methyl

Question 9

what is basicity

Answer 9

the extend to which a base can donate a lone pair of electrons to the hydrogen atom of a water molecule

Question 10

how can basicity be quantified (represented)

Answer 10

Kb or the constant pKb

Question 11

what is the Kb of water and what does that say about water

Answer 11

7 and it indicates that water is equally good as a base and as an acid

Question 12

the lower the pKb the

Answer 12

the greater the basicity of a substance

Question 13

increasing the hydrocarbon chain of a primary amine will cause the basicity

Answer 13

the basicity to increase, as the pKb decreases

Question 14

phenylamine is a weaker base compared with

Answer 14

water and the rest of the primary aliphatic amines

Question 15

why are the aliphatic amines better bases than ammonia

Answer 15

because the alkali groups are electron releasing and so there is an increases electron density on nitrogen compared with ammonia

Question 16

why propyl a better base than ethyl and ethyl is a better base than methyl

Answer 16

propyl is more electron releasing than ethyl and ethyl is more electron releasing than methyl so propyl > ethyl > methyl

Question 17

what is the equation for the reaction of butylamine with water

Answer 17

CH3CH2CH2CH2NH2 + H2O ⇌ CH3CH2CH2CH2NH3^+1 + OH^1-

Question 18

Why does phenylamine have week basicity

Answer 18

the original lone pair of electrons on nitrogen become part of the delocalized system of benzene so they become less available for the bonding to the hydrogen atom of a water molecule making nitrogen less electron rich (less of a nucleophile)

Question 19

all amines react with strong acids to form

Answer 19

strong bases (examples of reaction page 241

Question 20

once the nitrogen lone electron join the delocalized system in phenylamine what will surround the nitrogen

Answer 20

now the delocalized electrons will extend above and below nitrogen