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Chemistry (AS) > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

What is the functional group of an Alcohol

A

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

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2
Q

What is the General Formula of an alcohol

A

Cn H2n+1 OH

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3
Q

What type of intermolecular forces do alcohols have?

A

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

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4
Q

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

A

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

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5
Q

Explain Alcohols Solubility in water

A

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

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6
Q

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

A

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

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7
Q

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

the starting molecule for the mechanism is a Ethene

A

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

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8
Q

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

A

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

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9
Q

How can ethanol be made via fermentation

A

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

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10
Q

What are the advantages and disadvantages to ethanol production via Glucose

A
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11
Q

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

A

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

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12
Q

Draw a mechanism for the dehydration of a Primary Alchohol

A
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13
Q

Draw a mechanism for the dehydration of a secondary alcohol

A
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14
Q

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

A

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

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15
Q

What is the equation for ethanol combustion

A
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16
Q

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

A

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

17
Q

Why are Anti Bumping granules used in the oxidation of alcohols

A

To prevent vigorous bubbling / uneven boiling

18
Q

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

A

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

19
Q

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

A

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

20
Q

What is the set up for primary alcohol to Carboxilic Acid

A

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

21
Q

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

A
22
Q

What forms when you oxidise a secondary alcohol

A

Ketone

23
Q

Why can’t tertiary alcohols be oxidised

A

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

24
Q

What is tollens reagent how does it react?

A

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

25
Q

What is Fehlings how does it react?

A

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

26
Q

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

A

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

27
Q

What is the potassium dichromate colour change when reduced?

A

H2SO4 with K2Cr2O7

Goes from Orange —> Green (something has been oxidised)

Dichromate(IV) ions = Orange
Chromium(Cr3+) Ions = green

28
Q

List in Increasing Boiling point
Alcohol, Ketone, Alkene

A

Alkene->Ketone-> Alcohol

C=O is stronger then C=c

Alcohols can form hydrogen bonding

29
Q
A
30
Q

Describe Reflux

A

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

31
Q

How do you test for the presence of a Carboxylic acid

A

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

32
Q

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

A

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.

33
Q

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

A

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

34
Q

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

A

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

35
Q

You are distilling Propanal from a mixture of Propanal , Propanoic acid and Propan-1-ol

Explain two ways of maximising the yield of propanal

A

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

36
Q

Explain how carbon Dioxide Causes Global Warming.

A

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.

Chemistry (AS) (16 decks)

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