organic 3

Question 1

what is the amine functional group

Answer 1

C-NH2

Question 2

what is the amide functional group

Answer 2

C double bond O -NH2

Question 3

what is the amino acid functional group

Answer 3

amine+ carboxyl groups and hydrogen and R group attached to carbon

Question 4

why are amines boiling points lower than alcohols

Answer 4

oxygen in hydroxyl group is more electronegative than nitrogen therefore the hydrogen bonding in amines is weaker as there is less attraction between the nitrogen and hydrogen

Question 5

how many bonds with water can an amine make

Answer 5

3- one from nitrogen, 2 from hydrogens

Question 6

why are amines classed as weak bases

Answer 6

they have a lone pair on the N which can accept protons to form a conjugate acid

methylamine + H+ = methylammonium ion

Question 7

how do you increase the basicity of amines

Answer 7

add alkyl groups as they push electrons towards the nitrogen so they are able to accept more protons as higher electron density

Question 8

how can amines be prepared

Answer 8

1) halogenoalkanes by nucleophilic substitution
2) nitriles by reduction
3) aromatic nitro compounds by reduction

Question 9

haloalkane + ammonia reagents

Answer 9

excess NH3, heat in sealed container

Question 10

nitrile + H2 reagents

Answer 10

nickel catalyst

Question 11

aromatic nitro compound boil under reflux reagents

Answer 11

tin and conc HCl

Question 12

reactions of amines

Answer 12

amine + water -> ammonium salt + OH-
amine + acid -> ammonium salt
amine + acyl chloride -> N substituted amide
amine + halogenoalkane -> secondary amine

Question 13

how to make a polyamide from diacyl chloride and diamide

Answer 13

remove H from NH2 and one Cl to make HCl and connect molecules

Question 14

what does amphoteric mean

Answer 14

reacts as an acid and a base

Question 15

if you put an amino acid into basic solution, what will happen

Answer 15

carboxylic acid group deprotonates

Question 16

if you put an amino acid into a theoretically neutral solution, what will happen

Answer 16

H+ from COOH group forms bond with lone pair on N of NH2 group. this forms a zwitterion, an ion with both a permanent positive and negative charge, although overall the compound is neutral

Question 17

because amino acids are zwitterions, this gives them properties of…

Answer 17

high melting point solids
dissolve well in polar solvents
dissolve poorly in non polar solvents

Question 18

what is the isoelectric point of an amino acid

Answer 18

the point at which an amino acid exists as a zwitterion in solution

Question 19

what turns amino acid to an ester

Answer 19

ethanol with a few drops of sulfuric acid with warming

Question 20

benzene properties

Answer 20

colourless liquid
boiling point 80
carcinogenic
delocalised electrons

Question 21

what were the 4 problems with the Kekule structure of benzene

Answer 21

-benzene did not undergo addition reactions despite being unsaturated
-bond lengths were all the same
-carbons appear to be equivalent
-enthalpy of hydrogenation is too small

Question 22

is the enthalpy of hydrogenation of benzene less or more exothermic than a cyclic alkane

Answer 22

less exothermic

Question 23

what is resonance

Answer 23

the idea that the double bonds in benzene switch regularly to all merge together (pi ring)

Question 24

how does the 1.5 bond structure explain Kekules problems

Answer 24

1- bonds less electron dense so less susceptible to attack by electrophiles
2- same length as all 1.5
3- bromines on different carbons aren’t isotopes
4- thermodynamically more stable due to resonance energy

Question 25

why is benzene less reactive than alkenes

Answer 25

pi system less electron dense than a normal pi bond due to resonance less susceptible to attack by electrophiles

Question 26

combustion of benzene

Answer 26

usually incomplete burns with a smoky flame due to high carbon to hydrogen ratio

Question 27

hydrogenation of benzene

Answer 27

mix with hydrogen, heat under pressure with nickel catalyst

Question 28

what is good about electrophilic substitution of benzene

Answer 28

preserves pi system therefore preserves stability, swaps H for something else

Question 29

electrophilic substitution of benzene reagents conditions

Answer 29

add Cl2/Br2 and AlCl3 (halogen carrier)

Question 30

nitration of benzene

Answer 30

heat under reflux at 50 conc nitric acid and conc sulfuric acid

Question 31

what happens if temp goes over 50 in nitration of benzene

Answer 31

multiple substitutions will occur which is explosive

Question 32

friedel crafts reaction of benzene

Answer 32

AlCl3 and C2H5Cl anyhydrous conditions CH3COCl and AlCl3

Question 33

phenol properties

Answer 33

low solubility in water weakly acidic more reactive than benzene

Question 34

reactivity of phenol

Answer 34

lone pair of electrons on O of OH delocalises into pi system, increasing electron density more susceptible to electrophilic attack

Question 35

acidity of phenol

Answer 35

pi system overlap with O increases polarity of OH bond making H more likely to dissociate