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Chemistry 2.0 > 3.5 alcohols > Flashcards

3.5 alcohols Flashcards

1
Q

State name of H2C(OH)CN

A

2-hydroxyethanenitrile

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2
Q

State name of H2C(OH)CH2NH2

A

2-hydroxyethylamine

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3
Q

State name of H3CCH2CHO

A

propanal
*it is a aldehyde as the carbonyl is bonded to another hydrogen atom

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4
Q

State name of CH3COCH2CH2CH3

A

2-pentanone
*It is a ketone as carbonyl compound is bonded to two other carbon atoms

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5
Q

State name of H3CCH2COOH

A

Propanoic acid
*it is a carboxylic acid as carbonyl is bonded to an OH group

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6
Q

State the reaction equation of Direct hydration and state the reagents and conditions

A

CH2=CH2(g) +H2O (g) -> CH3CH2OH
Reagent : H2O
Conditions : concentrated phosphoric acid / SiO2 coated in H3PO4 catalyst
& High temperature & High pressure

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7
Q

Two main method for ethanol production

A

Direct hydration of ethene
Fermentation of glucose

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8
Q

State the reaction equation for fermentation
Also state the conditions needed

A

C6H12O6 -> 2CH3CH2OH + 2CO2
Conditions : enzymes from yeast
No air / no oxygen
Temperature of 30 - 40 degrees

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9
Q

Explain why neither a low temperature nor a high temperature is suitable for fermentation

A

Temperature too low: reaction too slow
* Temperature too high: destroys or denatures yeast enzyme

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10
Q

Give name of type of reaction involved in formation of the two alkenes

A

Elimination or dehydration

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11
Q

Butan-2-ol reacts with concentrated sulfuric acid to prodcue three isomeric alkenes
State mechanism
Explain how this reaction can lead to the formation of each of the three alkenes

A

Elimination
H+ ion is lost from the C, the carbocation that is adjacent to +C to which the -OH was attached to
Loss of H+ ion from the 1st carbon in the chain leads to but-1-ene
Loss of H+ ion from the 3rd carbon leads to but - 2 -ene
But-2-ene is formed as a mixture of E/Z isomers

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12
Q

Alcohol A is (CH3)2CHCH(OH)CH3. Name IUPAC name of structure of isomer A that cannot be dehydrated to form an alkene by reaction with concentrated sulfuric acid

A

H3CC(CH3)2CH2OH

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13
Q

A compound has the structural formula CH3CH2CH=CHCH2CH2OH
Give structural formula of organic product formed when this compound is dehydrated using concentrated sulfuric acid

A

CH3CH2CH=CHCH=CH2

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14
Q

Use equations to show that ethanol produced by fermentation is carbon neutral meaning no CO2 emissions are released into the atmosphere when using bio-ethanol as a fuel

A
  1. Photosynthesis:
    6CO2 + 6H2O → C6H12O6 + 6O2
  2. Fermentation:
    C6H12O6 → 2CH3CH2OH + 2CO2
  3. Combustion:
    2CH3CH2OH + 6O2 → 4CO2 + 6H2O
    * 6CO2 are taken in during photosynthesis
    * A total of 6CO2 are released during fermentation and combustion of ethanol
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15
Q

(use ethanol)
Write reaction equation for oxidation of a primary alcohol into into an aldehyde and an aldehyde turning into a carboxylic acid
State reagents and conditions for each reaction

A

Primary alcohol → Aldehyde
CH3CH2OH + [O] → CH3CHO + H2O
Reagent : acidified potassium dichromate (K2Cr2O7) - is represented by capital [O]
Conditions : Heat under distillation

Aldehyde → Carboxylic Acid
CH3CHO + [O] → CH3COOH
Reagent: Acidified K2Cr2O7
Conditions: Heat under reflux

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16
Q

(Use ethanol)
The oxidation of a primary alcohol to a carboxylic acid is a two-step process, but both steps can be done in one go. Show reaction equation, state reagents and conditions of a primary alcohol turning into a carboxylic acid

A

Reaction equation : CH3CH2OH + 2[O] → CH3COOH + H2O
Reagent: Acidified K2Cr2O7
Conditions: Heat under reflux, excess oxidising agent

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17
Q

Secondary alcohols can only be oxidised to ketones.
Show reaction equation, state reagents and conditions of oxidation of secondary alcohols (use propan-2-ol)

A

Reaction equation : CH3CH(OH)CH3 + [O] → CH3COCH3 + H2O
Reagent: Acidified K2Cr2O7
Conditions: Heat under reflux or distillation

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18
Q

Which alcohols cant be oxidised

A

Tertiary alcohols

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19
Q

State formula for when CH3CH2CH(OH)COOH reacts with acidified potassium dichromate (VI)

A

CH3CH2COCOOH

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20
Q

Butan-1-ol reacts with acidified potassium dichromate (VI). State the type of reaction that occurs and the change in colour of the
potassium dichromate(VI) solution.

A

Type of reaction is oxidation
Colour change : orange to green

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21
Q

State formula for butanedioic acid

A

HOOCCH2CH2COOH

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22
Q

Write an equation for this oxidation reaction of butane-1,4-diol into butanedionic acid (HOOCCH2CH2COOH)

A

HOCH2CH2CH2CH2OH + 4[O] -> HOOCCH2CH2COOH + 2H2O
*Hydrogens and oxygens must both be balanced

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23
Q

Explain why a water bath is used to heat a mixture of ethanol and acidified potassium dichromate and why it is preferred over a bunsen burner

A

Eliminate / reduce fire risk
as the alcohol is flammable

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24
Q

State purpose of glass beads in a flask

A

to prevent bumping

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25
Q

Student heats propan-1-ol with an excess of oxygen. State name of technique used

A

Fractional distillation

26
Q

Why are anti-bumping granules added to a reaction mixture

A

Prevents formation of large bubbles & to prevent vigorous boiling

27
Q

What happens to the aldehyde as it is produced during distillation

A

The aldehyde forms as a vapour and escapes from the reaction mixture into the condenser

28
Q

Why is distillation used when producing an aldehyde from a primary alcohol

A

Distillation allows the aldehyde to escape the reaction mixture and prevents further oxidation

29
Q

Ethanol can be oxidised to ethanal or ethanoic acid. Describe how ethanal can be made in high yield, as opposed to ethanoic acid

A

Use distillation
* Heat at the boiling point of ethanal
* Collect ethanal as it is distilled off

29
Q

propan-1-ol can be converted into propanoic acid in the laboratory.
Describe the experimental conditions and the practical method used to ensure that the acid is obtained in a high yield.
(b) Describe the different experimental conditions necessary to produce propanal in high yield rather than propanoic acid.

A

Excess acidified potassium dichromate
reflux must go on for a long time
(b) You must use fractional distillation s soon as the reagents are mixed

30
Q

Propan-1-ol is a volatile, flammable liquid. Give one safety precaution that should be used during the reaction to minimise this hazard

A

Keep away from naked flames
* you can have heat with a water bath

31
Q

Describe what happens when a reaction mixture is refluxed and why it is necessary, in this case, for complete oxidation to ethanoic acid.

A

A mixture of liquids is heated to boiling point for a prolonged time
Vapour is formed which escapes from the liquid mixture, is changed back into liquid and returned to the liquid mixture
Any ethanal and ethanol that initially evaporates can then be oxidised

32
Q

Write a half-equation for the overall oxidation of ethanol into ethanoic acid.

A

CH3CH2OH + H2O -> CH3COOH + 4H+ + 4e–

33
Q

The boiling points of the organic compounds in a reaction mixture are shown in the following table.

Compound ethanol, ethanal, ethanoic acid
Boiling point / °C 78, 21, 118
Use these data to describe how you would obtain a sample of ethanal from a mixture of these three compounds. Include in your answer a description of the apparatus you would use and how you would minimise the loss of ethanal
(b) explain why it is possible to separate ethanal in this way.

A

Mixture heated in a suitable flask / container
With still head containing a thermometer
Water cooled condenser connected to the still head and suitable cooled collecting vessel
Collect sample at the boiling point of ethanal
Cooled collection vessel necessary to reduce evaporation of ethanal

(b) Hydrogen bonding in ethanol and ethanoic acid and no hydrogen bonding in ethanal
Permanent dipole - dipole forces are weaker than hydrogen bonding

34
Q

Give two ways of maximising the yield of propanal obtained by distillation of the reaction mixture.

A

Keep temperature of reaction mixture below boiling point of propanol
Cool the distillate and collect the vessel

35
Q

What is the reagent used to test for aldehydes using a tollens reagent to oxidise an aldehyde
State observation when aldehyde is present and observation for when it is not present

A

Reagent : Tollens reagent
Aldehyde present : silver mirror forms
Aldehyde not present : no visible change

36
Q

What is the reagent used to test for aldehydes using fehlings solution to oxidise an aldehyde
State observation when aldehyde is present and observation for when it is not present

A

Reagent used to test for aldehydes: Fehling’s solution
· Observation when aldehyde present: brick-red precipitate
· Observation when aldehyde not present: No visible change

37
Q

What is the reagent used to test for carboxylic acids and state reagents for when carboxylic acid is present and not present

A

Reagent used to test for carboxylic acids: sodium carbonate / usually any carbonate works
Observation when carboxylic acid present: effervescence
Observation when carboxylic acid not present: No visible change

38
Q

State a reagent that could be added seperately to distinguish between an aldehyde and a carboxylic acid
State observations with the aldehyde and carboxylic acid

A

Reagent : Sodium carbonate
Observation with aldehyde : no visible change
Observation with carboxylic acid : effervescence

39
Q

State name of CH3CH2CH2COCH3

A

Pentan-2-one

40
Q

Give a reagent and observation for a test-tube reaction to distinguish between 2-methylbutan-1-ol and 2-methylbutan-2-ol

A

Reagent : potassium acidified dichromate
Observation with 2-methylbutan-1-ol : colour goes from orange to green
Observation with 2-ethylbutan-2-ol : no visible change

41
Q

Give a reagent and observation for a test-tube reaction to distinguish between Butan-2-ol and 2-methylpropan-2-ol

A

Reagent : Potassium acidified dichromate
Observation with butan-2-ol : Colour goes from orange to green
Observation with 2-methylpropan-2-ol : No visible change

42
Q

Give a reagent and observations to distinguish between aqeous silver nitrate and aqeous sodium nitrate

A

Reagent : hydrochloric acid / any soluble chloride
Observation with aqueous silver nitrate : wite precipitate formed
Observation with aqeous sodium nitrate : remains colourless

43
Q

Give a reagent and observation to distinguish between aqeous magnesium chloride and barium chloride

A

Reagent : Dilute sulfuric acid / any soluble sulfate
Observation with aqueous magnesium chloride : remains colourless / no observed change
Observation with aqeous barum chloride : White precipitate formed

44
Q

Butan-1-ol was oxidised by heating acidified potassium dichromate. State type of product distilled off during oxidation of the oxidation by acidified potassium dichromate (VI) solution

A

Aldehyde

45
Q

Compound D is a branched chain isomer of of butan-1-ol. It can be oxidised to form compound S and D. Compound S is obtained by distilling off as it forms during the oxidation. Compound T is formed when oxidation takes place under reflux. Identify functional groups of S and T

A

S : aldehyde/CHO T: Carboxylic acid/COOH

46
Q

Cyclohexene was made by heating cyclohexanol with phosphoric acid. The cyclohexene produced was distilles of the reaction mixture. Distillate was shaken with saturated sodium chloride solution. State why cyclohexene can be seperated from the aqeous solution using a seperating funnel

A

Liquids are immsicible

47
Q

Cyclohexene that was seperated from an aqeous solution was obtained as a cloudy liquid. Student dried cyclohexene by adding a few lumps of anyhdrous calcium chloride.
Give one observation that student made to confirm cyclohexene was dry

A

Liquid goes clear and wasnt cloudy

48
Q

Cyclohexene can be prepared by dehydration of cyclohexanol using concentrated phosphoric acid.
Describe a test-tube reaction,on the product, to show cyclohexanol has been dehydrated.
(b) Suggest why sodium carbonate solution was used to wash the distillate
(c) Apart from its ability to absorb water, what makes anyhdrous calcium chloride a suitable dyring agent in this preparation

A

Add bromine water
Solution will go from orange to colourless
(b) Sodium carbonate neutralises with phosphoric acid
(c) Doesnt dissolve in / react with cyclohexene

49
Q

In distillation why is it important to open the top periodically

A

Avoid pressure build up / release CO2 gas

50
Q

Cyclohexene is prepared by dehydration of cyclohexanol using concentrated phosphoric acid as a catalyst. Phosphoric acid and cyclohexanol both have hydrogen bonding and cyclohexene has vdw. State how cyclohexene can be seperated from the reaction mixture

A

vdw weaker than hydrogen bonding so cyclohexene has lower boiling point.
They are sperated using fractional distillation ad cyclohexene can be obtained fiest as it boils of first due to it having the lowest boiling point.

51
Q

State meaning of term carbon-neutral

A

An activity which has no overal annual carbon emmissions to the atmosphere

52
Q

Other than carbon-neutrality, state main advantage of the use of glucose from crops as the raw material for the production of ethanol

A

It is renewable

53
Q

State disadvantages of use of crops for production of ethanol

A

Requires use of fossil fuels /
Depletes food supply /
Slow rate of reaction, long time taken to grow crops /
This route leads to production of water and impure ethanol that requires further separating

54
Q

An industry decides to carry out fermentation at 35 degrees rather than 27 degrees. State one advantage and one disadvantage of of carrying out fermentation at a higher temperature

A

Advatnage : Ethanol produced at a quicker rate
Disadvantage : more energy is required for the reaction

55
Q

Ethanol produced by fermentation of glucose may be regarded as a carbon-neutral fuel. Justify this statement. Include relevant chemical equations in your answer

A

Reaction of photosynthesis :
6CO2 + 6H2O → C6H12O6 + 6O2
Reaction of fermentation : C6H12O6 → 2CH3CH2OH + 2CO2
Reaction of combustion : 2CH3CH2OH + 6O2 → 4CO2 + 6H2O
* 6C02 is taken in during photosynthesis
* Total of 6CO2 is taken out of fermentation and combustion of ethanol

56
Q

Suggest why ethanol produced in europe using silverskin from south america is less likely to be carbon-neutral than ethanol produced from crops grown in europe

A

Transport from south america to europe produces CO2 / has C emissions / has larger C footprint

57
Q

A statement said the fact that bioethanol is a cabron-neutral fuel outweighs the enviromental disadvantages of producing bioethanol. Evaluate this statement

A
  • Photosynthesis is the natural process in plants that takes CO2 from the air
  • Fermentation is the process used to make bioethanol releasing some CO2
  • Combustion is the process where bioethanol is burned and releases CO2
  • Write all equations
    Envirmental issues for cabron-neutrality :
  • Deforestation / Sacrifice land that could be used for food
  • Loss of biodiversity / habitat
  • 6CO2 comes in and out but t it isn’t actually C neutral as fuel is used in
    production, distribution etc
58
Q

2 advatnages of fermentation compared to direct hydration

A

Lower temperature and pressure / lower use of energy
Less use of non renewable fossil fuels
* DO NOT SAY CARBON-NEUTRAL

59
Q

3 ways of making ethanol are used
Combustion
direct hydration
fermentation
State why ethanol produced may not be a carbon-neutral biofuel

A

*A specified process e.g. planting / harvesting / transport / extracting sugar /
distilling ethanol solution / fertiliser production etc.
*The specified process uses / burns (fossil) fuel that releases CO2

60
Q

1-bromoethane turns into ethanol using nucleophilic substitution
Suggest why other than safety that method is not used to make ethanol

A
  • The yield is (very) low / not a high yield OR elimination occurs / ethene
    formed
  • The rate of reaction slow
  • Bromoethane has to be manufactured / made first

Chemistry 2.0 (9 decks)

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