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AS Chemistry > Biochemistry reactions > Flashcards

Biochemistry reactions Flashcards

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1
Q

Describe the three steps of radical substitution.

A
  1. Initiation
    -The production of free radicals.
  2. Propagation
    -The steps which produce products and more
    free radicals.
  3. Termination
    -Two free radicals meet to form a product.
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2
Q

Describe the difference between homolytic and heterolytic fission.

A

Homolytic fission involves the breaking of a covalent bond where both atoms leave with one electron from the shared pair.
Heterolytic fission is where one atom takes both electrons because it is more electronegative.

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3
Q

What mechanism is involved in halogenation of alkenes?

A

Electrophilic addition

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4
Q

Describe two sets of conditions needed for cracking.

A
  1. High temperate and high pressure

2. Lower temperature and ZEOLITE catalysts

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5
Q

Describe the reactants, products, and the necessary catalyst for hydration of an alkene.

A

Addition of water to an alkene, forming an alcohol. Catalyst of sulphuric acid / phosphoric acid.

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6
Q

Describe the necessary conditions, reactants and products formed for hydrogentation of alkenes.

A

Addition of hydrogen.
Catalyst such as nickel or platinum.
Product is corresponding alkane.
Conditions - around 4 atm at 150-250 degrees celcius.

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7
Q

What reactant is used in the oxidation of alkenes to diols?

A

Cold dilute, acidified solution of potassium permanganate.

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8
Q

What reactant is used for the further oxidation of diols to carboxylic acids or ketones?

A

Hot concentrated, acidified solution of potassium permanganate.

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9
Q

In the oxidation of diols with hot concentrated acidic potassium permangante, a single carbon fragment will yield what oxidised product?

A

Carbon dioxide.

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10
Q

In the oxidation of diols with hot concentrated acidic potassium permangante, a primary alcohol fragment will yield what oxidised product?

A

Carboxylic acid.

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11
Q

In the oxidation of diols with hot concentrated acidic potassium permangante, a secondary alcohol fragment will yield what oxidised product?

A

Ketone.

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12
Q

What is the mechanism involved in addition polymerisation?

A

Free radical.

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13
Q

Describe two methods of producing methanol.

A
  1. Hydrogenation of carbon monoxide with synthesis gas (200-300 degrees, 100 atm H2 gas) over a copper catalyst.
  2. Dry distillation of wood.
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14
Q

Describe a method of producing ethanol.

A

Fermentation of sugar using yeast enzyme.

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15
Q

How can any alcohol be formed?

A

From the hydration of alkenes using a catalyst of concentrated phosphoric acid.

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16
Q

What are the products of combustion of alcohols?

A

Water and carbon dioxide.

17
Q

What are the two most common oxidising agents for alcohols?

A

Acidified potassium dichromate and acidified potassium permanganate.

18
Q

What are some steps necessary to obtain a desired product of aldehyde when oxidising a primary alcohol, and how is it possible?

A

Use a mild oxidising agent (acidified potassium dichromate) / limited oxidising agent / excess alcohol and DISTILLATION. Aldehydes have low boiling points because of no hydrogen bonding.

19
Q

What will be the product of oxidising a secondary alcohol?

A

Ketone.

20
Q

What will be the product of oxidising a tertiary alcohol.

A

No product. Tertiary alcohols cannot be oxidised.

21
Q

What are the colour changes for two reagents which show a positive test for the oxidisation of a primary or secondary alcohol?

A

Acidified potassium dichromate - orange to green

Acidified potassium permanganate - purple to colourless

22
Q

What must be present in an alcohol&raquo_space; haloalkane substitution reaction for it to take place?

A

A strong acid.

23
Q

What is the product formed and catalyst required for a dehydration of an alcohol.

A

Alkene. Acid catalyst.

24
Q

Describe the steps to obtain an ester from an alcohol and a carboxylic acid. Name this reaction.

A

Esterification of alcohol with carboxylic acid. Requires concentrated sulfuric acid catalyst and reflux (because it is an equilibrium reaction).

25
Q

What is the main difference in terms of numbers of steps between SN1 and SN2 reactions?

A

SN1 reactions happen in two steps and SN2 happens in 1 step.

26
Q

What is Markovnikov’s rule?

A

The hydrogen atom in an HX compound bonds to the carbon with the most number of hydrogen atoms around it.

27
Q

What two reducing agents are used for the reduction of aldehydes or ketones to alcohols?

A

NaBH4, or LiAlH4 dissolved in ethanol.

28
Q

What type of reaction the is addition of HCN to aldehydes or ketones?

A

Nucleophilic addition.

29
Q

How can ammonia be obtained from an aldehyde / ketone?

A

Nucleophilic addition of HCN to aldehyde / ketone to create a hydroxynitrile. Then hydrolysis of the hydroxynitrile to form a carboxylic acid and ammonia.

30
Q

What test can be run for the presence of a carbonyl group?

A

Addition of 2,4-DNPH. Formation of orange ppt indicates carbonyl group.

31
Q

What tests indicated the presence of an aldehyde.

A

Fehling’s solution - reduced to red ppt.

Tollen’s reagenet - ‘silver mirror’ effect upon heating.

32
Q

How can a nitrile be obtained from an alkyl halide?

A

Nucleophilic substitution of an aklyl halide with NaCN / KCN dissolved in ethanol.

33
Q

How can an amine be obtained from an alkyl halide?

A

When an alkyl halide is reacted with ammonia dissolved in ethanol.

34
Q

How can an alcohol be obtained from an alkyl halide?

A

Hydrolysis of an alkyl halide with a mixture of water and ethanol.

35
Q

How can an alkene be obtained from an alkyl halide?

A

Elimination reaction when an alkyl halide is reacted with KOH / NaOH dissolved in ethanol.

36
Q

What solid catalyst can be used for the dehydration of an alcohol?

A

Aluminium oxide.

AS Chemistry (3 decks)

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