organic 2

Question 1

how do you identify/label a chiral carbon

Answer 1

with a star *

Question 2

what is an enantiomer

Answer 2

two optical isomers of the same molecule

Question 3

what is a racemic mixture

Answer 3

one with a 50:50 ratio mix of the two enantiomers

Question 4

what do two enantiomers do to plane polarised light

Answer 4

rotate it in opposite directions

Question 5

what would a racemic mixture do to plane polarised light

Answer 5

not rotate it as the rotations from each enantiomer cancel each other out - optically inactive

Question 6

what can you use to detect the rotation

Answer 6

a polarimeter

Question 7

Sn1 or Sn2 for tertiary, secondary and primary alcohols

Answer 7

tertiary - Sn1
secondary - both
primary - Sn2

Question 8

Sn1 or Sn2 for chlorine, iodine and bromine

Answer 8

iodine - Sn1 (larger atom so bond length is longer and therefore weaker)
bromine - both
chlorine - Sn2 (bond is strongest so must be broken first)

Question 9

what does sn1 and sn2 mean

Answer 9

sn1 has only 1 species reacting and 1 in rate equation (1st order)
sn2 has 2 species reacting and 2 in rate equation (2nd order)

Question 10

what happens in an sn2 mechanism of a chiral carbon

Answer 10

the optical activity is flipped as the OH attacks from the opposite side to the group leaving

Question 11

what are stereoisomers

Answer 11

molecules that have the same structural formula but a different arrangement of atoms in space (E-Z or optical)

Question 12

what are optical isomers

Answer 12

non-superimposable mirror images which rotate the plane of plane-polarised light in an equal amount but opposite directions

Question 13

what is plane polarised light

Answer 13

light that oscillates in one plane

Question 14

what is a polarimeter

Answer 14

used to measure the rotation of plane polarised light (by enatomiers)

Question 15

what is a chiral carbon

Answer 15

has 4 different groups bonded to it

Question 16

are aldehydes and ketones soluble in water

Answer 16

yes as they form hydrogen bonds w water w their oxygen

Question 17

do they form hydrogen bonds with themselves

Answer 17

no as they do not have a delta positive hydrogen

Question 18

potassium dichromate test

Answer 18

orange-> green if oxidised

tertiary alcohols/ ketones remain orange

Question 19

Fehlings test

Answer 19

blue-> red ppt (aldehydes only)

Question 20

Tollens test

Answer 20

colourless-> silver mirror (aldehydes only)

Question 21

how to reduce ketones/aldehydes or carboxylic acid back to alcohol

Answer 21

add LiAlH4 in dry ether conditions as it can react violently

Question 22

how to make a hydroxynitrile and why are they made

Answer 22

react aldehyde or ketone with HCN in presence of KCN
(nucleophilic addition)

used in chemical synthesis to extend carbon chain

Question 23

why is a racemic mixture produced when adding HCN

Answer 23

CN nucleophile can attack from either side of the plane as carbon is trigonal planar- both enantomiers made

Question 24

why is KCN often used over HCN

Answer 24

HCN is hard to store and a toxic gas which produces dangerous by-products

Question 25

iodoform test

Answer 25

add iodine add NaOH until colour of iodine disappears yellow ppt forms if COCH3 is present

Question 26

2,4 DNPH test

Answer 26

add 2,4 DNPH orange ppt forms can recrystallise ppt to work out boiling point of hydrazone

Question 27

are carboxylic acids soluble in water

Answer 27

yes they form hydrogen bonds with water molecules

Question 28

can carboxylic acids bond to themselves

Answer 28

yes it forms hydrogen bonds with itself

Question 29

how can carboxylic acids be neutralised

Answer 29

add a base (NaOH or NH3) and will produce a salt and maybe water

Question 30

what is a derivative of carboxylic acid

Answer 30

acyl chloride

Question 31

how do you form an acyl chloride

Answer 31

carboxylic acid + PCl5 -> acyl chloride + POCl3 + HCl

Question 32

how to make an ester

Answer 32

alcohol plus carboxylic acid in presence of acid catalyst remove OH from acid and H from alcohol, produces water

Question 33

properties of esters

Answer 33

sweet smelling used in perfume or food flavouring low boiling points good solvents for polar molecules

Question 34

4 reactions of acyl chlorides

Answer 34

+water -> carboxylic acid +alcohol -> ester +ammonia -> amide +amines -> N substituted amide

Question 35

how does hydrolysis of esters differ in different conditions

Answer 35

acidic (H+ and H2O) -> acid + alcohol alkaline -> carboxylate salt + alcohol

Question 36

what is carboxylate salt used for and what is the process called

Answer 36

used for soap as it has hydrophobic and hydrophilic properties process called saponification

Question 37

how to make a condensation polymer

Answer 37

dicarboxylic acid + dialcohol both OH on acid removed both H on alcohol removed

Question 38

how are condensation polymers good for the environment

Answer 38

can be broken down through hydrolysis due to polarity so are biodegradable and can be put into landfill

Question 39

what is optical activity

Answer 39

ability of a single optical isomer to rotate the plane of polarisation of plane polarised light in molecules containing a single chiral centre

Question 40

carboxylic acid with LiAlH4

Answer 40

produce primary alcohol nucleophilic addition dry ether conditions as very reactive

Question 41

carboxylic acid with base

Answer 41

neutralisation produce salt + water

Question 42

carboxylic acid with PCl5

Answer 42

acyl chloride, POCl3 and HCl

Question 43

acyl chloride functional group

Answer 43

C-O-Cl

Question 44

ester functional group

Answer 44

COO

Question 45

name the role of HCl in esterification reaction

Answer 45

catalyst

Question 46

3 differences between esterification of alcohol+acid and alcohol+acyl chloride

Answer 46

acyl chloride reaction is irreversible Hcl byproduct instead of water the reaction is very fast and occurs at room temp so catalyst is not needed

Question 47

reflux ester with NaOH

Answer 47

produces carboxylic acid and alcohol when heated

Question 48

why is a molecule sparingly soluble in water

Answer 48

talk about London forces and hydrogen bonding

Question 49

3 differences in acid and alkali hydrolysis of esters

Answer 49

-acid is catalyst not reagent -acid produces carboxylic acid, alkali carboxylate salt -acid is reversible reaction so produces lower yield

Question 50

carboxylic acid plus sodium carbonate

Answer 50

carboxylate salt + water + carbon dioxide