Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chem Mock > Alcohols > Flashcards

Alcohols Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

Alcohols are a family of….

A

molecules that contain the hydroxyl functional group, -OH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

general formula

A

CnH2n+1OH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does the complete combustion of alcohol produce

A

carbon dioxide and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Three ways to convert alcohols to halogenoalkanes

A

Chlorination

Bromination

Iodination

replacing the hydroxyl group in an alcohol molecule with a halogen atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

explain chlorination

A

Phosphorus(V) chloride is added to alcohol at room temperature

phosphoryl chloride and hydrogen chloride

CH3CH2CH2OH + PCl5 → CH3CH2CH2Cl + POCl3 + HCl

Chlorination of tertiary alcohols can be carried out in a different way by mixing (shaking) with hydrochloric acid at room temperatureThis reaction will not occur with primary or secondary alcohols.
(CH3)3CCl + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

explain bromination

A

warmed mixture of potassium bromide and 50% concentrated sulfuric acid with the reacting alcohol

2KBr + H2SO4 → K2SO4 +2HBr

CH3CH2CH2CH2OH + HBr → CH3CH2CH2CH2Br + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

explain iodination

A

using a mixture of red phosphorus and iodine with the alcohol whilst heating under reflux

2P + 3I2 → 2PI3

3C2H5OH + PI3 → 3C2H5I + H3PO3

formation of phosphoric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is dehydration

A

done by heating the alcohol with concentrated phosphoric acid
similar to the elimination reaction of a halogenoalkene
The OH group and hydrogen of adjacent carbons are removed forming a C=C bond

CH3CH2OH → CH2=CH2 + H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can primary alcohols oxidise to form

A

form aldehydes which can undergo further oxidation to form carboxylic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Secondary alcohols can be oxidised to form

A

ketones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what do tertiary alcohols form when oxidised

A

do not undergo oxidation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the oxidising agents of alcohols

A

Acidified potassium dichromate(VI), K2Cr2O7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what happens to dichromate ions when alcohols are oxidised

A

When alcohols are oxidised the orange dichromate ions (Cr2O72-) are reduced to green Cr3+ ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what happens when primary alcohol is added to oxidising agent and warmed

A

The aldehyde product has a lower boiling point than the alcohol reactant so it can be distilled off as soon as it forms

If the aldehyde is not distilled off, further refluxing with excess oxidising agent will oxidise it to a carboxylic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what about ketone when distilling off

A

Since ketones cannot be further oxidised, the ketone product does not need to be distilled off straight away after it has been formed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

formula for carboxylic acid

A

CnH2n+1COOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

formula for aldehydes

A

CnH2n+1CHO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Ketone formula

A

CnH2nO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how can you determine -OH group

A

If you add PCl5 to an unknown liquid the evolution of steamy fumes (HCl gas)

20
Q

how can you determine the presence of an aldehyde group

A

oxidising agent Fehling

should go to red precipitate otherwise remain blue

21
Q

what is Feeling’s solution

A

alkaline solution containing copper(II) ions which act as the oxidising agent

22
Q

what happens when feelings solution is warmed with aldehyde

A

aldehyde is oxidised to a carboxylic acid and the Cu2+ ions are reduced to Cu+ ions

The carboxylic acid formed will be neutralised to a carboxylate ion (the -COOH will lose a proton to become -COO- )

The carboxylate ion (-COO-) will form a salt with a positively charged metal ion such as sodium (-COO-Na+)

clear blue solution turns opaque due to the formation of a red precipitate, copper(I) oxide

23
Q

Can you do Fehling’s solution on ketone

A

Ketones cannot be oxidised and therefore give a negative test when warmed with Fehling’s solution

24
Q

What is Tollens’ reagent

A

aqueous alkaline solution of silver nitrate in excess ammonia solution

25
Q

what happens when Tollens is warmed with an aldehyde

A

the aldehyde is oxidised to a carboxylic acid and the Ag+ ions are reduced to Ag atoms

In the alkaline conditions, the carboxylic acid will become a carboxylate ion and form a salt

The Ag atoms form a silver ‘mirror’ on the inside of the tube

26
Q

two techniques for oxidising aldehydes

A

Heating under reflux
Distillation with addition

27
Q

what is heating under reflux

A

Producing a carboxylic acid for a primary alcohol
Producing a ketone for a secondary alcohol

any products of oxidation remain in the reaction mixture
Products which boil off condense in the vertical condenser then return to the heating flask

28
Q

what does condenser help with

A

ensure vapour condense and return to the flask for further heating.

29
Q

what is distillation with addition

A

when we do not want to complete oxidation
To obtain an aldehyde rather than carboxylic acid for primary alcohol

30
Q

what is simple distillation

A

separate a liquid and soluble solid from a solution

or a pure liquid from a mixture of liquids

31
Q

what is fractional distillation

A

separate two or more liquids that are miscible with one another

32
Q

what is solvent extraction and conditions

A

This method uses a solvent to remove a desired organic product from a reaction mixture

Immiscible (does not mix) with the solvent containing the desired organic product

The desired organic product should be much more soluble than the added solvent

33
Q

process of solvent extraction

A

Place the reaction mixture in a separating funnel and add the chosen solvent forming a separate layer

Place a stopper in the neck of the funnel and gently shake the contents of the funnel for a while

Allow the contents of the funnel to settle into two layers

Remove the stopper and open the tap to allow the lower layer to drain into a flask

Pour the remaining layer into a clean dry conical flask and add two spatulas of anhydrous magnesium sulfate
This will remove water
It should be added until there is no further clumping and it can then be removed by gravity filtration

34
Q

explain crystallisation

A

separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold

The solution is heated, allowing the solvent to evaporate, leaving a saturated solution behind

The saturated solution is allowed to cool slowly
Crystals begin to grow as solids will come out of solution due to decreasing solubility
The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry

35
Q

how can you test if the solution is saturated after crystallisation

A

dipping a clean, dry, cold glass rod into the solution
If the solution is saturated, crystals will form on the glass rod

36
Q

what happens to temperature from impurities

A

Impurities present in the liquid will raise its boiling temperature

37
Q

Can you do tollens reagent on Ketones

A

Ketones cannot be oxidised and therefore give a negative test when warmed with Tollens’ reagent

38
Q

what is stereoisomerism

A

compounds with same structural formula but atoms have different arrangement

39
Q

how to achieve high yield of aldehyde

A

distill off immediately

40
Q

give one reason why yield is less than 100%

A

transfer loss
incomplete reaction
side reactions

41
Q

6 test for alcohols
reagents and observations

A

bromine water - orange / yellow / brown solution goes colourless

carboxylic acid and H2SO4 - smell of an ester

acidified potassium manganate - purple to colourless

alkaline potassium manganate - purple to green

neutral potassium manganate - purple to brown

acidified potassium dichromate - orange to green

42
Q

how can you obtain pure dry sample of cyclohexene

when reacting cyclohexanol with phosphoric acid and this mixture is warmed in water bath for 15 minutes before distilling the mixture of cyclohexene and water

A

separate cyclohexene from water using separating funnel

IP2 remove the lower aqueous layer because it has a higher density
* IP3 suitable drying agent
* IP4 separate the cyclohexene from the drying agent
* IP5 redistil product
* IP6 collect the distillate boiling over between 80 and 86 °C to
collect the pure cyclohexene

43
Q

how can alcohol be converted to nitrile

A

via intermediate product called
1-bromobutane

halogenoalkane is heated under reflux with a solution of sodium or potassium cyanide in ethanol. The halogen is replaced by a -CN group and a nitrile is produced

44
Q

why do anti bumping granules give a smoother boil

A

because it provides a surface area for bubbles to form and prevent large bubbles from forming

45
Q

hydrogen bromide plus alcohol

what is
cooling a mixture
antibumping granules
heating under reflux used for

A

cool the mixture because the reaction (with concentrated sulfuric acid /
H2504) is (very) exothermic

anti-bumping granules are added to prevent violent / sudden / localised boiling

to make sure the vapour / gas condenses
Or
to prevent vapour escaping
(1)

46
Q

describe how to dry the organic layer to prepare for distillation

A

add magnesium sulfate and leave until solution becomes clear and drying agent dont clump together

47
Q
A

Chem Mock (34 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions