6E -ALCOHOLS

Question 1

general formula for alcohols? (1)

Answer 1

• CnH2n+1OH

Question 2

what 3 types of alcohols can you get and how ?

3

Answer 2

• primary alcohol =OH attached to carbon with 1 other C attached ( 1 r group)
• Secondary alcohol = OH attached to carbon attached to 2 Carbons ( 2 r groups )
• Tertiary alcohol=OH attached to Carbon (with 3 r groups)

Question 3

Alcohol +Oxygen (combustion )

Answer 3

-CO2 +H2O

Question 4

Alcohol+PCl5 or HCl ? produces?
which type of alcohol is fastest ?
(3)

Answer 4

• CHLOROALKANE
• nucleophilic substitution
• fastest with tertiary alcohol (sn1 mechanism favoured)

Question 5

how do you make bromoalkanes ?(3)

Answer 5

• Bromoalkane
• ALCOHOL + 50% CONC sulphuric acid +KBr
• ACID CATALYST

Question 6

how do you make iodoalkanes ?(3)

Answer 6

• red phosphorous and iodine
  -reflux alcohol with red phosphorus and iodine to produce insitu PI3
  General Equation : 3ROH + PI3 —>3RI +H3PO3

Question 7

How can you form an Alkene from an Alcohol ?

4

Answer 7

• DEHYDRATION REACTION (elimination where water is eliminated )
• Alcohol + Acid Catalyst such as CONCENTRATED phosporic acid (H3PO4)
• heated !
• water is eliminated

Question 8

what will primary alcohols oxidise to ? (1)

Answer 8

• aldehydes –> carboxylic acids

Question 9

what will secondary alcohols oxidise to ? (1)

Answer 9

-KETONES

Question 10

what will tertiary alcohols oxidise to ? (1)

Answer 10

• They WON’T

Question 11

what is the general formula for an Aldehyde or Ketone ?

1

Answer 11

-CnH2nO

Question 12

What is an aldehyde? (1)

Answer 12

• one alkyl group attached to carbonyl carbon atom C=O

Question 13

what is a ketone ? (1)

Answer 13

-have two alkyl groups attached to carbonyl carbon atom

Question 14

How can you test for Aldehydes and ketones?

4

Answer 14

• Benedicts solution = cu2+ dissolved in sodium carbonate
  =aldehyde = turn from blue to brick red ppt
  cu2+ ions reduced
  -Fehling’s solution :
  =blue to red in aldehydes
  =contains cu2+ dissolved in sodium Hydroxide

Question 15

how can you make a aldehyde from a Primary alcohol ?

5

Answer 15

• OXIDISE WITH POTASSIUM DICHROMATE
• distill to get Aldehyde
• gently heating excess alcohol with controlled amount o Potassium Dichromate
• distillation apparatus
• so aldehyde which boils at lower temp is distilled of immediately .

or you could gently heat with alcohol with potassium dichromate and H2SO4 in test tube –> aldehyde –>carboxylic acid

Question 16

how can you make a carboxylic acid from a primary alcohol ?

2

Answer 16

• vigourous OXIDATION WITH POTASSIUM DICHROMATE

- REFLUX

Question 17

How can you make ketones ?(2)

Answer 17

• acidified Potassium DICHROMATE

- REFLUX

Question 18

how can you oxidise tertiary alcohols ?(1)

Answer 18

• Burn them

Question 19

why do we reflux? (2)

Answer 19

• condenses vapours giving the substance time to react

- also makes sure you down lose any volatile substances .

Question 20

why do we carry out distillation? (1)

Answer 20

• separate products based on bp

Question 21

how do we determine impurities ? (2)

Answer 21

• Boiling points- thermometer on distillation

- if the value is higher than data book value = IMPURITIES!

Question 22

How do we remove traces of water ?

2

Answer 22

• add drying agent = ANHYDROUS SALT i.e. : MgSO4 BINDS TO WATER = HYDRATED and takes away water !
• filter away after

Question 23

How do we make Alkenes from alcohols ?

2

Answer 23

• dehydration reaction

- heat with strong acid such as h2so4 or phosphoric acid