topic 6e: alcohols

Question 1

primary alcohol

Answer 1

OH group bonded to a C bonded to only 1 other carbon atom

Question 2

combustino of alcohols produces

Answer 2

carbon dioxide and water (complete)

Question 3

halogenation

Answer 3

-OH is replaced bya halogen

Question 4

how to holgenate to add chlorine

Answer 4

PCL5

Question 5

ALCOHOLS REACTION WITH pcl5 product

Answer 5

• POCl3 + HCl + chloroalkane
• STEAMY FUMES OF HCl

Question 6

alcohols + PCl5 observation

Answer 6

steamy fumes (HCl gas)

Question 7

chlorination of TERTIARY Alcohols

Answer 7

• shake with HCl at room temp
• forms compound + H2O

Question 8

how to do iodination

Answer 8

• red phosphorus + iodine
• heat under reflux
• 2P + 3I2 = 2PI3
• alc + PI3 = halkane + h3po3

Question 9

products of iodination

Answer 9

1. haloalkane
2. H3PO3
   (phosphoric acid)

Question 10

how to dehydrate alcohol (elimination)

Answer 10

• heat with a concentratred phosphoric acid
  forms an alkene

Question 11

dehydration (elimination) alcohol product

Answer 11

alkene + water

Question 12

primary alcohols oxidise to …

Answer 12

ALDEHYDES (then to carboxylic acids)

Question 13

seconadry alcohols oxidise to

Answer 13

KETONS

Question 14

tertiary alcohols oxidise to

Answer 14

do not oxidise

Question 15

usual oxidisiing agent

Answer 15

acidified potassium dichromate
K2Cr2O7 in DILUTE sulfuric acid

Question 16

colour change oxidation of alcohols

Answer 16

orange (cr207)2- to green cr3+

Question 17

cr2o7 2- colour

Answer 17

orange

Question 18

cr 3+ colour

Answer 18

green

Question 19

how to bromonate

Answer 19

• potassium bromide + 50% sulfuric acid to form HBr. REFLUXXXXXXXXX
• HBr + alc = halkane + h2o

Question 20

reaction for potassium bromide + 50% conc sulfuric acid

Answer 20

2KBr+H2SO4 = K2SO4 + 2HBr

Question 21

why does aldehyde need to be distilled off as soon as its formed

Answer 21

so it doesnt further oxidise to a carboxylic acid

Question 22

heating under reflux

Answer 22

• FULL OXIDATION eg carboxylic acid from primary, keton from secondary
• products of oxidation remain in the reaction mixture; condense and then return to the heating flask
• OPEN TOP!!!!!!

Question 23

DISTILLATION

Answer 23

• PARTIAL oxidation eg aldehyde from primary alcohol
• aldehyde is dsitilled off as its formed, (lower BP than alcohol)
• collected in the receiver

Question 24

what to change to go from distillation to heat under reflux

Answer 24

• open top condsner
• vertical condenser

Question 25

why is x more soluble in ETHANOL than in WATER (2)

Answer 25

- water has 2 h bonds/ molecule, ethanol only 1 - h bonding in water stornger, requires more enegy to break

Question 26

why is yield low of the aldehyde when heating under reflux?

Answer 26

- aldehyde is condesned - fully oxidises to a carboxylic acid

Question 27

purpose of anti bumping granules

Answer 27

-provides a surface for bubbles to form - PREVENTS LARGE BUBBLES FROM FORMING

Question 28

why are SMALL alcohols soluble in water?

Answer 28

- h bonds in water and in alcohols - of similar strenght - therefore h bonds form between the 2

Question 29

why are larger alcohols less soluble?

Answer 29

- proporition of molecule that can H Bond is smaller - LF in alcohol stronger -

Question 30

ethanol from ethene (hydration of ethene)

Answer 30

- ethene + steam - phosphoric (V) acid CATALYST - 300 degrees - 60-70 atmospheres

Question 31

ethanol can also be made by...

Answer 31

fermentation

Question 32

stereoisomers (2)

Answer 32

- same structural formula - sifferent arrangement in space

Question 33

3 reasons for lower yeild

Answer 33

- transfer losses (residue left on apparatus) - incomplete - side reactions

Question 34

why not use distillation to produce carboxylic acid

Answer 34

- produces aldehyde - aldehyde will distil as soon as produced (before it turns into carboxylic acid)

Question 35

how to dry organic layer to preapre for distillation (2)

Answer 35

- mix with drying agent eg anhydrous cacl2 - leave until adding drying agent doesnt clump together

Question 36

how to improve distillation

Answer 36

- add antibumbing granules - surface for bubbles to form -thermometer should be opposite entrance of condenser - collecting over wrong temperature range - add more ice water -

Question 37

why add sodium hydrogen carbonate in the experiment?

Answer 37

- react with HCl - to release CO2

Question 38

drying agent

Answer 38

sodium sulfate calcium chloride

Question 39

thermometer in experiment distillation must be

Answer 39

OPPOSITE TO OPENING OF CONDENSER

Question 40

in reactions, water enters the ... of the condsner

Answer 40

BOTTOM

Question 41

conical flask in distillation must be ...

Answer 41

open

Question 42

why no stopper in reflux?

Answer 42

so pressure doesnt build up

Question 43

why might you se brown vapour in bromonation?

Answer 43

- Br2 gas produced -bromide ions have been oxidised by the acid

Question 44

why add HCl in the experiment?

Answer 44

remove any unreacted alcohol

Question 45

why open tap from time to time?

Answer 45

prevent build up of pressure (allow co2 to escape)

Question 46

explain why reaction is slow, then speeds up, then slows

Answer 46

- slow due to repulsion - speeds up as mn2+ autocatalytic - slows down cos conc reactants decreases

Question 47

fermentation

Answer 47

glucoe = ethanol +co2

Question 48

fermentation conditions

Answer 48

- anaerobic - yeast - 25-42 degrees c

Question 49

why can fermentation thought to be NOT carbon neutral

Answer 49

co2 emissions with vehicles for transporting

Question 50

how to turn a halogenoalkane into an alcohol

Answer 50

- sodium hydroxide - aqueous - heat under reflux NUCLEOPHILIC SUBSTIUTION

Question 51

HYDRATION OF ETHENE name of mechanism

Answer 51

electrophilic addition

Question 52

WHY DONT TERTIARY OXIDISE

Answer 52

- no H atom on central carbon

Question 53

why hydration of ethene over fermentation

Answer 53

- fast reaction - purer product2

Question 54

alkene to diol

Answer 54

add acidified potassium 2 manganate (H3PO3)