Alcohols

Question 1

What is the functional group of an Alcohol

Answer 1

hydroxyl group -OH
If there is somthing of higher priority that takes the suffix use Hydroxy

Question 2

What is the General Formula of an alcohol

Answer 2

Cn H2n+1 OH

Question 3

What type of intermolecular forces do alcohols have?

Answer 3

Hydrogen Bonding, Dipole-Dipole and VDW
Due to the electronegative difference polarising the O-H bond, producing a permanent dipole so strong it forms weak bonds with surrounding molecules

Question 4

How do alcohols mp and bp compare with hydrocarbons of similar carbon chains

Answer 4

Higher because they have hydrogen bonding & dipole dipole intermolecular forces that arestronger then only van det waaaa forces within hydrocarbon chains due to no polar bonds

Question 5

Explain Alcohols Solubility in water

Answer 5

Soluble in short carbon chain alcohols, insoluble in long.
As carbon chain increases solubility decreases.
-polar OH group means that hydrogen binding can occur between the lone pair and a polar water molecule but not the hydrogen carbon chain

Question 6

Draw all Alcohol types and What makes each of them it.

Answer 6

Primary: C bonded to the OH and no other R groups
Secondary: C bonded to the OH and 1 other R groups
Tertiary: C bonded to the OH and all other bonds are to carbons

Question 7

How do you turn a Alkene to an Alcohol include catalysts equations and mechanism

the starting molecule for the mechanism is a Ethene

Answer 7

Hydration of ethane via Electrophilic addition
H3PO4 Acid Actalyst
Steam
200-450 Degrees
60-70Atm
C2H4 + H20 (reversible) C2H5OH

Question 8

What are the Advantages & Disadvantages to ethanol production via Ethene steam and acid catalyst

Answer 8

Advantages: Fast, continuous process, ethanol has a high purity
Disadvantages: non renewable due to curde oil

Question 9

How can ethanol be made via fermentation

Answer 9

glucose with the presence of yeast catalyst in no oxygen
35 Degrees
No oxygen
C6H12O6(aq) —> 2( C2H5OH) + 2( CO2)

Question 10

What are the advantages and disadvantages to ethanol production via Glucose

Answer 10

Question 11

How do you make ethene from an Alcohol include catalysts and any conditions

Answer 11

Dehydration of An alcohol
under reflux
elimination reaction
Conc H2SO4 acid catalyst

Question 12

Draw a mechanism for the dehydration of a Primary Alchohol

Answer 12

Question 13

Draw a mechanism for the dehydration of a secondary alcohol

Answer 13

Question 14

How could using ethanol in petrol engines could be considered carbon neutral (biodiesel)

Answer 14

Carbon dioxide released in fermentation and combustion = Carbon dioxide absorbed when growing
However local transport of the good after manufacture , use of combine harvesters to harvest the plant.

would not make it neutral

Question 15

What is the equation for ethanol combustion

Answer 15

Question 16

Draw the Apparatus and explain dehydration of an alcohol to alkene via aluminium oxide

Answer 16

Alcoholic vapours pass over heated Aluminium(III) oxide to form an Alkene

Question 17

Why are Anti Bumping granules used in the oxidation of alcohols

Answer 17

To prevent vigorous bubbling / uneven boiling

Question 18

Why is a heating element or water bath used for the oxidisation of alcohols

Answer 18

Use of a Bunsen burner would ignite alcoholic vapours escape which is dangerous

Question 19

Explain how do partially oxidise an alcohol to an aldehyde include diagram

Answer 19

1) A solution of acidified potassium dichromate (VI) and sulphuric acid is diluted so less is available then needed for complete oxidisation
2) Add solution to alcohol and heat via water bath for gentle heating
The beaker at then end is cooled with ice to reduce the evaporation of the product due to a low boiling point

Thermometer is placed at the centre of the delivery tube to measure vapour temperature as they leave
A Liebig condenser is placed in the delivery tube

Question 20

What is the set up for primary alcohol to Carboxilic Acid

Answer 20

Concentrated sulphuric acid
ACIDIFIED Potassium dichromate
Reflux for 20 mins strong heating
Open top

Question 21

1)What is the general equation for 1)Alcohol-> Carboxilic
2) Alcohol -> aldehyde

Answer 21

Question 22

What forms when you oxidise a secondary alcohol

Answer 22

Ketone

Question 23

Why can’t tertiary alcohols be oxidised

Answer 23

You need to be able to remove a hydrogen from the OH group and a singular hydrogen connected to the same carbon to form water
Which is impossible in a tertiary alcohol as there are no C-H bonds on that carbon

Question 24

What is tollens reagent how does it react?

Answer 24

Silver nitrate with 1 drop of sodium hydroxides in excess NH3(aq)
Oxidised aldehydes not ketones
Complex silver (I) ions are reduced to a silver precipitate which forms a silver mirror within the test tube

Question 25

What is Fehlings how does it react?

Answer 25

Heat Blue copper (II) complex ions - gentle oxidising agent is reduced to Cu+ ions which is the colour of brick red if there is an alcohol or aldehyde present

Question 26

Why in industry isn’t Haloalkanes and Nucleophilic Substitution used to make Ethanol

Answer 26

Too slow rate of reaction Bromoethane has to be manufactured first and is expensive Very low yield as elimination occurs easily and ethene is formed from bromoethane

Question 27

What is the potassium dichromate colour change when reduced?

Answer 27

H2SO4 with K2Cr2O7 Goes from Orange —> Green (something has been oxidised) Dichromate(IV) ions = Orange Chromium(Cr3+) Ions = green

Question 28

List in Increasing Boiling point Alcohol, Ketone, Alkene

Answer 28

Alkene->Ketone-> Alcohol C=O is stronger then C=c Alcohols can form hydrogen bonding

Question 29

Answer 29

Question 30

Describe Reflux

Answer 30

A mixture of liquids heated to a boiling point for a prolonged time Vapour is formed which escapes from the liquid mixture. Vapours travel immediately into a condenser vapours condense back into a liquid and returns to the reaction mixture

Question 31

How do you test for the presence of a Carboxylic acid

Answer 31

Add Sodium Carbonate (test for acids) If effervescence then there is an acid present

Question 32

Explain How an elimination reaction with a methyl alcohol produces products of not equal quantities

Answer 32

The mechanism of reaction involves the formation of a carbocation 2 possible carbocations form, 1 leading to formation of the major product and 1 leading to formation of. the minor product. The carbocation leading to the major product, is more likely to form as its more stable. This is due to the positive inductive effect of the methyl group on the major carbocation.

Question 33

Explain How Distillation can prepare a pure sample of an aldehyde from an Alcohol

Answer 33

Alcohol is oxidised to from an aldehyde, using a oxidising agent not in excess Aldehyde boiling point is lower then an alcohol, so it forms vapours first. Reaction mixture is heated to Aldehyde Boiling point Only Aldehyde Vapours rise to the condenser, they condense and are collected in a beaker

Question 34

How would you change the set up from distillation of an Alcohol to Reflux

Answer 34

1) Add excess Oxidising agent 2) Place condenser vertically above round bottom flask 3) leave hole at the top of the condenser to prevent pressure buildup

Question 35

You are distilling Propanal from a mixture of Propanal , Propanoic acid and Propan-1-ol Explain two ways of maximising the yield of propanal

Answer 35

1) Cool collection vessel with an ice bath 2) Keep temperature below the boiling point of propan-1-ol

Question 36

Explain how carbon Dioxide Causes Global Warming.

Answer 36

C=O bonds in CO2 absorb infrared radiation of 2350 cm^-1 cosmic IR radiation reflected by the earth doesn’t escape from the atmosphere. This energy is transferred to other molecules in the Atmosphere by collisions, so all atmosphere is warmed.