Chapter 14 - Alcohols Flashcards Preview

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Flashcards in Chapter 14 - Alcohols Deck (26)
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1
Q

What is the functional group of alcohols?

A

-OH

2
Q

Why do alcohols, with few carbon atoms, have much higher boiling points than alkanes, with more carbon atoms?

A

Alcohols can form strong hydrogen bonds between the O and the neighbouring hydrogen atoms in a molecule, therefore; require more energy to break.

3
Q

How do alcohols and alkanes compare in volatility if they have the same number of carbon atoms?

A

alcohol will be less volatile.

4
Q

Why are alcohols soluble in water?

A

The polar OH bond forms hydrogen bonds with the water molecules.

5
Q

As hydrocarbon chain increases, how does solubility of alcohols change?

A

It decreases as the OH group’s influence becomes relatively small and solubility shifts to that of alkanes.

6
Q

What is a primary alcohol?

A

The OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group.

7
Q

What kind of alcohol is methanol?

A

Although misleading it is a primary alcohol.

8
Q

Describe what are secondary and tertiary alcohols?

A

Secondary: OH attached to carbon attached to two alkyl groups
Tertiary: OH attached to carbon attached to three alkyl groups

9
Q

The combustion of alcohols has what products?

A

Carbon dioxide and water

10
Q

What is used to oxidise alcohols?

A

Potassium dichromate

11
Q

What are the two forms of chromium in oxidation reactions?

A

Dichromate(VI) ions that are orange

Chromium(III) ions that are green

12
Q

Which two products can be formed from the oxidation of primary alcohols?

A

Aldehydes or carboxylic acids

13
Q

How are aldehydes prepared from the oxidation of primary alcohols?

A

Gentle heating of primary alcohols with acidified potassium dichromate.

14
Q

What measure is taken to ensure no carboxylic acid is made?

A

Aldehyde is distilled out of the mixture as it forms to prevent any further reaction.

15
Q

How are carboxylic acids prepared from the oxidation of primary alcohols?

A

Primary alcohol is heated strongly under reflux with an excess of acidified potassium dichromate.

16
Q

Why is it under reflux for carboxylic acid preparation?

A

To ensure any aldehyde initially formed also undegoes oxidation to the carboxylic acid.

17
Q

What product is formed from the oxidation of secondary alcohols?

A

Ketones

18
Q

How are ketones prepared from the oxidation of secondary alcohols?

A

Heated under reflux with acidified potassium dichromate.

19
Q

What product is formed from the oxidation of tertiary alcohols?

A

Tertiary alcohols do not undergo oxidation reactions.

20
Q

What is dehydration?

A

Any reaction in which a water molecule is removed from the starting material.

21
Q

What are the conditions of a dehydration reaction?

A

Alcohol is heated under reflux in the presence of concentrated sulfuric acid or phosphoric acid.

22
Q

What are the products of a dehydration reaction?

A

An alkene and water

23
Q

Alcohols react with hydrogen halides to form what?

A

Haloalkanes and water

24
Q

What are the conditions of a halogen substitution reaction of an alcohol?

A

Alcohol is heated under reflux with sulfuric acid and a sodium halide, the hydrogen halide is formed in situ.

NaBr + H2SO4&raquo_space;> NaHSo4 + HBr

The hydrogen halide reacts with the alcohol to form a haloalkane and water

propan-2-ol + HBr –> 2-bromopropane + H2O

Overall eqn:
CH3CHOHCH3 + NaBr + H2SO4 –> CH3CHBrCH3 + NaHSO4 + H2O

(propan-2-ol + Sodium Bromide + Sulfuric Acid –> 2-bromopropane + Sodium Hydrogen Sulfate + Water)

25
Q

what is alcoholic fermentation

A

Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products.

C6H12O6 → 2C2H5OH + 2CO2

26
Q

what is the two large scale method to form alcohol

A

Fermentation, using yeast, of sugars, such as glucose, C6H12O6.
C6H12O6(aq) → 2C2H5OH(aq) + 2CO2(g)

Hydration of ethene, C2H4, with steam in the presence of an acid catalyst.
C2H4(g) + H2O(g) → C2H5OH(g)