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A-level Chemistry > Synthesis routes > Flashcards

Synthesis routes Flashcards

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1
Q

How is the carbon chain extended when synthesising new compounds?

A

Refluxing the alkane with potassium cyanide in ethanol to form a nitrile. Turning the nitrile into an amide and then hydrolysing it, forming a carboxylic acid

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2
Q

Reducing a phenylketone

A

Reduce using NaBH4 to break the C=O bond and add 2 hydrogens

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3
Q

Aromatic amine + halogen

A

Replaces H with halogen at positions 2, 4, and 6

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4
Q

Amine + acid

A

N forms a dative covalent bond with the proton, making a quaternary salt

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5
Q

Amino acid carboxylic group + base

A

Water + sodium carboxylate salt

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6
Q

Amino acid carboxylic group + alcohol

A

Water + ester made from COOH of amino acid

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7
Q

Amino acid carboxylic group + metal ion

A

Metal carboxylate salt + hydrogen/CO2/water

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8
Q

Amino acid amine group + acid

A

Quaternary amine salt

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9
Q

Amino acid amine group + R-X

A

R added to nitrogen, H+ removed, H+ and X- left over

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10
Q

Primary amide + hot acid and water

A

Carboxylic acid + ammonium ion

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11
Q

Secondary amide + hot acid and water

A

Carboxylic acid + RNH3+

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12
Q

Primary amide + Hot OH- and water

A

Carboxylate + ammonia

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13
Q

Secondary amide + Hot OH- and water

A

Carboxylate + RNH2

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14
Q

Preparation of aromatic amines

A

Nitrobenzene + Sn + conc HCl under reflux => Phenylamine

ArNO2 + 6[H] + HCl => ArNH3+ + Cl- + 2H2O
ArNH3+ + Cl- + NaOH => ArNH2 + NaCl + H2O

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15
Q

Reduction of nitriles

A 
A reducing agent turns the -C≡N group into -C-NH2
Agents:
anhydrous LiAlH4: 4[H]
anhydrous Na (alcohol): 4[H]
Ni (catalyst): 2H2
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16
Q

How can you control the major product of the reaction between haloalkanes and ammonia?

A

Excess ammonia means the major product is the primary amine

Excess haloalkane means the major product is the quaternary salt

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17
Q

Formation of an aliphatic amine

A

Haloalkane + anhydrous ethanol + NH3 => Halide ion + Amine salt
Halide ion + amine salt + OH- => Amine + H2O + Halide ion

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18
Q

Extending the carbon chain

A

Reflux a solution of the haloalkane, potassium cyanide and ethanol
C-Cl becomes C-C≡N

C-C≡N can be reduced to an amine
H2O and H+ turns C-C≡N into CONH2
H2O and H+ turns CONH2 into COOH

19
Q

CH3COOH + SOCl2 =>

Anhydrous conditions

A

CH3COCl + SO2 + HCl

20
Q

Overall reaction of acyl chlorides (RCOCl)

A

RCOCl + HX => RCOX + HCl

HX can be water, an alcohol, phenol, ammonia, or an amine

21
Q

What happens in the initiation stage of the halogenation of an alkAne?

A

The UV light splits the halogen molecule into 2 radicals (Br₂ => 2Br•)

22
Q

What happens in the propagation stage of the halogenation of an alkAne?

A

Radicals react with non-radicals, building up the products of the reaction

C₂H₆ + Br• => •C₂H₅ + HBr
•C₂H₅ + Br₂ => C₂H₅Br + Br•

23
Q

What happens in the termination stage of the halogenation of an alkAne?

A

The radicals come together to form stable products

2Br• => Br₂
2•C₂H₅ => C₄H₁₀
•C₂H₅ + Br• => C₂H₅Br

24
Q

Hydrogenation of an alkEne

A

Converts alkEne to alkAne

C₂H₄ + H₂ => C₂H₆

150 degrees, nickel

25
Q

Hydration of an alkEne

A

Acid and steam, produces an alcohol.

26
Q

How do you determine the major product of a reaction between a hydrogen halide and an asymmetrical alkene?

A

Use Markownikoff’s rule: The hydrogen bonds to the carbon atom already bonded to the most hydrogens to begin with. This is because carbocations with other carbons bonded to the C+ are more stable, meaning they react less easily

27
Q

What happens when a primary alcohol is fully oxidised by K2Cr2O7?

A

Water and a carboxylic acid are formed

28
Q

What happens when a secondary alcohol is heated under reflux with K2Cr2O7?

A

Water and a ketone are formed

29
Q

What happens when you gently heat a primary alcohol with an oxiding agent (such as K2Cr2O7), and distil immediately?

A

The alcohol is partially oxidised to an aldehyde, and water is formed

30
Q

Describe esterification

A

An alcohol and a carboxylic acid react in the presence of an acid catalyst to form an ester. This reaction is slow and reversible.

31
Q

What happens when an alcohol is heated with a strong acid?

A

The -H and the -OH are removed from the carbon backbone, forming water and an alkene

32
Q

How are esters formed in the lab?

A

Alcohol and carboxylic acid mixed in test tube. Sulfuric acid is added and the tube is kept in a hot water bath

33
Q

How are alcohols dehydrated in the lab?

A

Alcohol is heated under reflux with sulfuric or phosphoric acid for 40 minutes

34
Q

How do hydrogen halides react with alcohols?

A

They form a haloalkane and water.

35
Q

How can you predict the product of the dehydration of an alcohol?

A

Primary alcohol => One alkene
Secondary alcohol => Two alkenes (stereoisomers)
Tertiary alcohol => No reaction

36
Q

Describe the nitration of benzene

A

Warm benzene is added to concentrated nitric acid and sulfuric acid. This releases electrophilic NO2+ ions into the solution. An electron from the delocalised electron ring in the benzene molecule bonds the NO2+ to one of the carbons. The H bonded to the same carbon donates its electron back to the delocalised ring and becomes a free H+ ion

37
Q

How can you form a salt from phenol?

A

Phenol is weakly acidic, so it reacts with NaOH to form sodium phenoxide and water. It also does the same with sodium.

38
Q

What are the conditions for making chlorobenzene?

A

Chlorine gas and solid aluminium chloride (completely anhydrous)

39
Q

How is nitromethylbenzene produced from benzene?

A

Benzene requires nitration and alkylation. The nitro group is 3-directing, whereas the methyl group would be 2, 4 and 6-directing.

40
Q

Describe the nitration of phenol

A

Phenol reacts with dilute nitric acid to form two isomers of nitrophenol, and water. Due to the increased reactivity of phenol compared to benzene, it doesn’t require a catalyst

41
Q

What is Friedel-Crafts alkylation?

A

A reaction that puts an alkyl group (such as methyl) on a benzene ring using a haloalkane and a halogen carrier. The reaction is C6H6 + RX + AlCl3 => (reflux) C6H5R + HCl

42
Q

What is Friedel-Crafts acylation?

A

A reaction that substitutes a H in benzene for an acyl group. The reaction is C6H6 + RCOCl + AlCl3 => (reflux) C6H5COR + HCl. If R is a hydrogen, the product is benzaldehyde, otherwise it’s a phenylketone

43
Q

Carbonyl + acid + cyanide

A

=O becomes -OH, CN added

A-level Chemistry (8 decks)

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