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AS Level Chemistry > Alcohols simplified > Flashcards

Alcohols simplified Flashcards

1
Q

What is the general formula for an alcohol

A

Cn H2n+1 OH

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2
Q

Something to look out for

A

When naming if there is a higher priority functional group than -OH use the prefic hydroxy e.g. O=C-C-O-H(this is an aldehyde)
!
H
Would be 2-Hydroxy Ethanal
Also the hydroxyl group takes priority over alkyl groups and halogen subsituents as well as doouble bonds in the numbering of parent chains

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3
Q

What is the Symbol equation for Hydration(ethene is used as an example)

A

C2=CH2 + H2O → CH2(OH)-CH23
A hydroxyl group (OH−) attaches to one carbon of the double bond, and a proton (H+) adds to the other. The reaction is highly exothermic

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4
Q

What are the conditions required for Hydration(3)

A
  • High temperature
  • High pressure
  • Phosphoric acid catalyst (represented as H+)
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5
Q

What are the disadvantages of Hydration(3)

A
  • High technology equipment required which costs money
  • Ethene is a non renewable resource so will runn out one day
  • High energy costs for pumping to produce high pressures
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6
Q

Advanages of HYDRATION

A
  • Faster reaction
  • Purer product
  • Continuous process
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7
Q

What regeant is required for hydration

A

Ethene

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8
Q

What is the Balanced symbol equatin of Fermentation

A

C6H12O6 (aq)–> 2C2H5OH(aq) + 2CO2(g)

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9
Q

What are the conditions required for fermentation

A
  • Yeast
  • Anaerobic conditions -no oxygen- (because oxygen could cause extra reactions- it oxidises the ethanol produced to ethanoic acid (vinegar)
  • Temp of 30-40 (38 is optimum temp)
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10
Q

What happens if the temperature is too high or too low in fermnetation

A

Too low: Reaction will be very slow
Too high:Yeast dies and enzymes denature

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11
Q

Advantages of fermentation

A
  • Sugar is a renewable resource
  • Production uses low level technology
  • Cheap equipment
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12
Q

Disadvantages of fermentation

A
  • Batch process which is slow and gives high production costs
  • Ethanol made is impure and needs purifying by fractional distillation
  • Depletes land as crops need land
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13
Q

What is the Dehydration of ethanol

A

The removal of water from ethanol also known as an elimination reaction

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14
Q

What are the steps in the dehydration of ethanol

A
  1. Draw arrow from the lone pairs on the O in the alcohol to the H+(Catalyst)
  2. H gets added to the hydrocl group which forms RC-O-H2 (O becomes positive)
  3. A H from the next carbon over gives an electron to the C (draw arrow from H to the C
  4. Draw arrow from C to the O
  5. You get your product (ooverall reation =Alkene + water + H+
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15
Q

What is a biofule

A

A biofuel is a fuel produced from plants

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16
Q

Define carbon neutral

A

The term carbon neutral refers to “an activity that
has no net annual carbon (greenhouse gas)
emissions to the atmosphere”

17
Q

Why is ethanol a biofuel

A

It can be argued that ethanol produced from this method is classed as
carbon–neutral because any carbon dioxide given off when the biofuel is
burnt would have been extracted from the air by photosynthesis when the
plant grew. There would be no net CO2 emission into the atmosphere.

18
Q

Equations to show no net contribution to CO2

A

6 CO2 + 6 H2O –> C6H12O6 + 6 O2 -6 CO2 molecules are removed from the atmosphere when the plants grow by photosynthesis to produce one molecule of glucose.

C6H12O6 –> 2 CH3CH2OH + 2 CO2 -When 1 molecule of glucose is fermented 2 molecules of CO2 is emitted.
2 CH3CH2OH + 6O2 –> 4 CO2 + 6 H2O -The two ethanol molecules produced will then produce 4 molecules of CO2 when they are combusted.

Overall for every 6 molecules of CO2 absorbed, 6 molecules of CO2 are emitted. There is no net contribution of CO2 to the atmosphere.

19
Q

What are the conditions, Reagents Role of reagent and type of reaction for the reaction: Alcohol —> Alkene

A

Reagents: Conc sulfuric acid or phosphoric acid
Conditions: Warm under reflux
Role of reagents: Dehydrating agent/Catalyst
Type of reaction: Acid catalysed elimination

20
Q

What is an example of the products given out when the double bond forms between different carbon atoms in secondary and tertiary alcohols

A

For example Butan 2 ol can give you But 1 ene and But 2 ene which can also exist as E-Z isomers

21
Q

Fact

A

Producing alkenes from alcohols provides a possible route to polymers without using monomers derived from oil

22
Q

What are the conditions, Reagents, Role of reagent and type of reaction for the oxidation of secondary alcohols

A

Reaction: Secondary alcohol —>Ketone
Reagent: potassium dichromate solution and dilute sulfuric acid
Conditions: heat under reflux

23
Q

Naming for ketone

A

When ketones have 5C’sor more in a chain then it needs a number to show the position of the double bond. E.g. pentan-2-one

24
Q

Word equation for how you get a ketone
And what is the observation

A

Propan-2-ol + [O] —> Propanone(CH3C=OCH3) +H2O

Observation: the orange dichromate ion (Cr2O7^2-) reduces to the green Cr 3+ ion

There is no further oxidation of the ketone under these conditions.

25
Q

Can tertiary alcohols be oxidised?

A

Tertiary alcohols cannot be oxidised at all. This is because there is no hydrogen atom bonded to the carbon with the -OH group.

26
Q

How do you distinguish between Aldehydes and Ketones

A
  • Aldehydes can be further oxidised to carboxylic acids whereas ketones cannot be further oxidised.
  • This is the chemical basis for two tests that are commonly used to distinguish between aldehydes and ketones.
27
Q

What are the two reagents used when testing whether an alcohol is a ketone or an aldehyde

A

Reagent: Tollens’ reagent formed by mixing
aqueous ammonia and silver nitrate. The
active substance is the complex ion of
[Ag(NH3)2]+

Reagent: Fehling’s solution containing blue Cu 2+ ions.

28
Q

What are the conditions required for both the reagents used when testing for an aldehyde or ketone

A

Conditions: heat gently

29
Q

What is the reaction (aldehyde only) in tollens reagent

A

oxidised by Tollens’ reagent into a carboxylic acid. The silver(I) ions are reduced to silver atoms

30
Q

What is the reaction (aldehyde only) in Fehlings solution

A

oxidised by Fehling’s solution into a carboxylic acid. The copper (II) ions are reduced to copper(I) oxide .

31
Q

What are the observations for tollens reagent

A

Observation: with aldehydes, a silver mirror
forms coating the inside of the test tube.
Ketones result in no visible change

CH3CHO + 2Ag+ + H2O —-> CH3COOH + 2Ag + 2H+

32
Q

What are the observations for Fehlings solution

A

Observation: Aldehydes :Blue Cu 2+ ions in
solution change to a red precipitate of Cu2O.
Ketones do not react

CH3CHO + 2Cu2+ + 2H2O —> CH3COOH + Cu2O + 4H+

33
Q

How can carboxylic acids be tested

A

By the addition of sodium carbonate. It will fizz and produce carbon dioxide.

AS Level Chemistry (14 decks)

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