Chemistry- organic synthesis

Question 1

what is reflux

Answer 1

technique used to heat volatile liquids

Question 2

how does reflux work

Answer 2

strongly heated without losing volatile reactants and products. Volatile compounds evaporate and condense -falls back into the flask

Question 3

what does volatile mean

Answer 3

how easily a substance will vaporize

Question 4

how does a liebig condenser work

Answer 4

cold water running through wall, hot evaporating substances turn back into a liquid and return back to round bottomed flask.

Question 5

how do we need to be careful when using flammable liquids

Answer 5

use water bath or electric heater: mantle

Question 6

what is distillation

Answer 6

used to separate substances with different boiling points

Question 7

how does distillation work

Answer 7

gently heating mixture will result in the compounds separating out in order of boiling point. knowing the boiling point of the chemical will allow you to decide how to separate the compound

Question 8

what will happen if the compound has lower boiling point than starting mixture

Answer 8

heat to the temp of boiling point of the compound

collect product in a separate vessel

Question 9

what will happen if the compound has higher boiling point than starting mixture

Answer 9

heat to temp of boiling temp of compound

product will remain on the round bottomed flask

Question 10

what is distillation useful for

Answer 10

useful when you want to extract a chemical before it reacts any further.

Question 11

example of distillation

Answer 11

oxidising primary alcohols can produce aldehydes however if aldehyde isn’t removed as soon as its formed it will oxidise to form a carboxylic acid

Question 12

what is filteration

Answer 12

used to separate solids and liquids

Question 13

what does the vacuum do

Answer 13

used to help separate liquid and solid components thoroughly.
vacuum creates reduced pressure in flask and pulls liquid through
Solid is left in the buchner funnel

Question 14

how do we purify this further?

after distillation

Answer 14

recrystallisation

Question 15

what is recrystallisation

Answer 15

method to purify solids

-solvent chosen is very important

Question 16

steps for recrystallisation

Answer 16

1. add enough solvent, impure solid dissolves
2. cool the solution down slowly, crystals will start to form
3. impurities will remain dissolved in solution takes longer for them to crystallise
4. filter collects purified crystals, wash in cold solvent to dry of

Question 17

why do we choose the solvent carefully

Answer 17

want impure solid to dissolve fully in hot solvent but be insoluble when its cold. if substance doesn’t dissolve in hot solvent, cant be purified further

Question 18

what does measuring boiling point detect

Answer 18

detects impurities

Question 19

how to carry out distillation to determine boiling point

Answer 19

1- gently heat sample, can then measure temperature at which it distils using thermometer
2.then compare this boiling point with data book value

Question 20

how do we know if sample contains impurities

Answer 20

• if boiling point is higher than what is in data book

- sample boils over a range of temperatues

Question 21

what is needed to be done if compounds have same boiling points

Answer 21

need to use analytical techniques such as mass spectrometry to spot impurities

Question 22

how can purity of a compound be measured

Answer 22

can be determined by measuring the melting point

Question 23

how to carry out purification

Answer 23

1. add sample of solid into capillary tube and place into heating element
2. slowly increase temperature until substance starts to melt
3. temperature ranges from when it begins to melt to when it fully melts
4. compare melting points (using data book values)
5. if substance contains impurities the melting point will be lower and temp range substance melts at will be higher

Question 24

alkanes

Answer 24

properties: unreactive, non-polar bond
Reactions: radical substitution

Question 25

alkene

Answer 25

properties: non-polar bond
reactions: electrophilic addition

Question 26

aromatic compounds

Answer 26

properties: delocalised ring
reaction: electrophilic substitution

Question 27

alcohols

Answer 27

properties: lone pair on oxygen turns into nucleophile, polar C-OH bond
reactions:
- esterification + nucleophilic substitution

Question 28

haloalkane

Answer 28

properties: polar c-x bond
reactions: nucleophilic substitution + elimination

Question 29

what are the 7 different reaction types

Answer 29

• addition reaction
• substitution reaction
• elimination/dehydration
• condensation reaction
• hydrolysis
• oxidation
• reduction

Question 30

addition reaction

Answer 30

double bond is broken, 2 molecules join together to form single product
functional groups involved: alkene, ketone, aldehydes

Question 31

substitution reactions

Answer 31

functional group is exchanged for another one

functional groups: halogens, benzene, alcohol

Question 32

elimination-dehydration

Answer 32

double bond is formed when a functional group is removed and released as part of a smaller molecule

Question 33

condensation reaction

Answer 33

when two molecules join and small molecule is eliminated

carboxylic acid, amide, alcohol, acid chlorines

Question 34

hydrolysis

Answer 34

2 smaller molecules formed by splitting lager one with water (breaking polyamides and polyesters)

Question 35

oxidation

Answer 35

loss of electrons

1) primary alcohol to aldehydes to carboxylic acid
2) secondary alcohol to ketone

Question 36

reduction

Answer 36

gain of electrons

primary alcohol to aldehydes to carboxylic acid