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AH Chemistry > 3.2 - Synthesis > Flashcards

3.2 - Synthesis Flashcards

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1
Q

explain basically bond fission

A

bonds in reactant molecules are broken and bonds in product molecules are made

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2
Q

what are the 2 types of bond fission

A

homolytic and heterolytic

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3
Q

what type of reaction does bond fission occur in?

A

organic

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4
Q

what does homolytic fission form

A

2 neutral radicals

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5
Q

what type of bond usually allows homolytic fission to occur?

A

a non-polar, sigma covalent bond

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6
Q

what happens in homolytic fission

A

each atom retains 1 electron when the bond is broken

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7
Q

why is homolytic fission unsuitable for organic synthesis

A

the reaction results in a very complex mixture of products

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8
Q

what does heterolytic fission form

A

2 oppositely charged ions

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9
Q

what type of bond allows heterolytic fission to occur

A

polar, sigma covalent bonds

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10
Q

what happens in heterolytic fission

A

1 atom retains both electrons when the bond is broken

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11
Q

what makes heterolytic fission suitable for organic synthesis

A

the reaction results in far fewer products than in homolytic fission

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12
Q

a single-headed arrow indicates

A

the movement of a single electron

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13
Q

a double-headed arrow indicates

A

the movement of an electron pair

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14
Q

the tail of the arrow shows

A

the source of the electron(s)

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15
Q

the head of the arrow indicates

A

the destination of the electron(s)

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16
Q

two single-headed arrows starting at the middle of a covalent bond indicate

A

homolytic bond fission is occurring

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17
Q

a double-headed arrow starting at the middle of a covalent bond indicates

A

heterolytic bond fission is occurring

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18
Q

an arrow drawn with the head pointing to the space between two atoms indicates

A

that a covalent bond will be formed between those two atoms

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19
Q

what are the 2 types of attacking group

A

nucleophiles and electrophiles

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20
Q

what are nucleophiles “rich” in

A

electrons

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21
Q

give examples of nucleophiles

A

Cl⁻ Br⁻ OH⁻ CN⁻ NH₃ H₂O

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22
Q

what are nucleophiles attracted to

A

atoms bearing a partial or full positive charge

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23
Q

what are nucleophiles capable of

A

donating an electron pair to form a new covalent bond

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24
Q

electrophiles are deficient in what

A

electrons

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25
Q

give examples of electrophiles

A

H⁺ NO₂⁺ SO₃

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26
Q

what are electrophiles attracted to

A

atoms bearing a partial or full negative charge

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27
Q

what are electrophiles capable of

A

accepting an electron pair to form a new covalent bond

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28
Q

what does e-anchors stand for

A 
 elimination
 addition
 neutralisation
 condensation
 hydrolysis
 oxidation
 reduction
 substitution
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29
Q

what is the maximum number of steps needed to devise a synthetic route for a given reactant to a final product

A

3

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30
Q

how is a haloalkane (alkyl halide) created

A

one or more hydrogen in an alkane is substituted for a halogen atom

31
Q

what is a monohaloalkane

A

a haloalkane which contains 1 halogen atom

32
Q

what do monohaloalkanes form in an elimination reaction

A

alkenes

33
Q

what is used in the monohaloalkane elimination reaction

A

a strong base such as potassium or sodium hydroxide in ethanol

34
Q

nucleophilic substitution of a monohaloalkane with aqueous alkalis forms what

A

alcohols

35
Q

nucleophilic substitution of a monohaloalkane with aqueous alcoholic alkoxides forms what

A

ethers

36
Q

nucleophilic substitution of a monohaloalkane with ethanolic cyanide forms what

A

nitriles (chain length increases by one) (these can be hydrolysed to carboxylic acids)

37
Q

what are the 2 types of nucleophilic substitution mechanism

A

Sₙ1 and Sₙ2

38
Q

explain Sₙ1 nucleophilic substitution

A
  • has 1 species in its rate determining step

- occurs in a minimum of 2 steps via a trigonal planar carbocation intermediate

39
Q

explain Sₙ2 nucleophilic substitution

A
  • has 2 species in the rate determining step

- occurs in a single step via a single five-centred, trigonal bipyramidal transition state

40
Q

how can alcohols be prepared

A

 haloalkanes by substitution
 alkenes by acid-catalysed hydration (addition)
 aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride

41
Q

how are alcohols dehydrated to alkenes

A

using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid

42
Q

how are alcohols oxidised to form aldehydes then carboxylic acids / ketones

A

using acidified permanganate, acidified

dichromate or hot copper(II) oxide

43
Q

what does an alkoxide contain

A

O⁻

44
Q

how are alcohols made into alkoxides

A

reaction with some reactive metals such as potassium or sodium

45
Q

what catalysts can be used in the formation of ethers from alcohols and carboxylic acids

A

concentrated sulfuric acid or concentrated phosphoric acid

46
Q

what is the functional group in an acid chloride

A

COCl (C=O / C-Cl)

47
Q

what catalysts need to be used in the formation of esters from alcohols and acid chlorides?

A

no catalysts are needed

48
Q

which is a faster reaction, ester formation from alcohol and carboxylic acid, or alcohol and acid chloride

A

alcohol and acid chloride

49
Q

how is an alkyl group formed from an alkane

A

one hydrogen is removed

50
Q

what is the general structure for substituted alkane ethers

A

R’ - O - R” where R’ and R’’ are alkyl groups

51
Q

what can ethers be regarded as

A

substituted alkanes

52
Q

how is an ether formed

A

a hydrogen is removed from an alkane, and is replaced with an alkoxy group

53
Q

describe a process in which an ether is produced

A

the nucleophilic substitution reaction between a monohaloalkane and an alkoxide

54
Q

which ethers are soluble in water

A

methoxymethane and methoxyethane

55
Q

what type of ethers are insoluble in water and why

A

large ethers, as they have a large molecular size

56
Q

why are ethers commonly used as solvents

A

they are relatively inert chemically and will dissolve many organic compounds

57
Q

how can alkenes be prepared

A
  • dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
  • base-induced elimination of hydrogen halides from monohaloalkanes
58
Q

what electrophilic addition reactions can alkenes take part in

A
  • with hydrogen to form alkanes in the presence of a catalyst
  • with halogens to form dihaloalkanes
  • with hydrogen halides to form monohaloalkanes
  • with water using an acid catalyst to form alcohols
59
Q

what does Markovnikov’s rule state

A

that when a hydrogen halide or water is added to an unsymmetrical alkene, the hydrogen atom becomes attached to the carbon with the most hydrogen atoms already attached to it.

60
Q

which product formed follows Markovnikovs rule

A

the major product

61
Q

how can carboxylic acids be produced

A
  • oxidising primary alcohols using acidified permanganate, acidified dichromate and hot copper (ii) oxide
  • oxidising aldehydes using acidified permanganate, acidified dichromate, Fehling’s solution and Tollens’ reagent
  • hydrolysing nitriles, esters or amides
62
Q

reactions of carboxylic acids include:

A
  • formation of salts by reactions with metals or bases
  • condensation reactions with alcohols to form esters in the presence of concentrated sulfuric/phosphoric acid
  • reaction with amines to form alkylammonium salts that form amides when heated
  • reduction with lithium aluminium hydride to form primary alcohols
63
Q

how are amines formed

A

1 or more hydrogen atoms from ammonia are replaced by an alkyl group

64
Q

are amines acidic or basic

A

basic

65
Q

which amines display hydrogen bonding

A

primary and secondary

66
Q

are amines strong or weak bases

A

weak

67
Q

how do amines produce hydroxide ions with water

A

the nitrogen atom has a lone pair of electrons which can accept a proton from water

68
Q

what is the chemical formula for benzene

A

C6H6

69
Q

what is the simplest member of the class of aromatic hydrocarbons

A

benzene

70
Q

why is benzene stable

A

the delocalisation of electrons in the conjugated system

71
Q

why does benzene not take part in addition reactions

A

delocalised electrons are present

72
Q

how is a phenyl group formed

A

one hydrogen atom is substituted for another group in a benzene molecule

73
Q

what is the formula for a phenyl group

A

-C6H5

74
Q

Benzene rings can take part in electrophilic substitution reactions. Reactions at benzene rings include:

A

 halogenation by reaction of a halogen using aluminium chloride or iron(III) chloride for chlorination and aluminium bromide or iron(III) bromide for bromination
 alkylation by reaction of a haloalkane using aluminium chloride
 nitration using concentrated sulfuric acid and concentrated nitric acid
 sulfonation using concentrated sulfuric acid

AH Chemistry (10 decks)

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