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AH Chemistry > 3.2 - Synthesis > Flashcards

3.2 - Synthesis Flashcards

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
give examples of electrophiles
H⁺ NO₂⁺ SO₃
26
what are electrophiles attracted to
atoms bearing a partial or full negative charge
27
what are electrophiles capable of
accepting an electron pair to form a new covalent bond
28
what does e-anchors stand for
```  elimination  addition  neutralisation  condensation  hydrolysis  oxidation  reduction  substitution ```
29
what is the maximum number of steps needed to devise a synthetic route for a given reactant to a final product
3
30
how is a haloalkane (alkyl halide) created
one or more hydrogen in an alkane is substituted for a halogen atom
31
what is a monohaloalkane
a haloalkane which contains 1 halogen atom
32
what do monohaloalkanes form in an elimination reaction
alkenes
33
what is used in the monohaloalkane elimination reaction
a strong base such as potassium or sodium hydroxide in ethanol
34
nucleophilic substitution of a monohaloalkane with aqueous alkalis forms what
alcohols
35
nucleophilic substitution of a monohaloalkane with aqueous alcoholic alkoxides forms what
ethers
36
nucleophilic substitution of a monohaloalkane with ethanolic cyanide forms what
nitriles (chain length increases by one) (these can be hydrolysed to carboxylic acids)
37
what are the 2 types of nucleophilic substitution mechanism
Sₙ1 and Sₙ2
38
explain Sₙ1 nucleophilic substitution
- has 1 species in its rate determining step | - occurs in a minimum of 2 steps via a trigonal planar carbocation intermediate
39
explain Sₙ2 nucleophilic substitution
- has 2 species in the rate determining step | - occurs in a single step via a single five-centred, trigonal bipyramidal transition state
40
how can alcohols be prepared
 haloalkanes by substitution  alkenes by acid-catalysed hydration (addition)  aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride
41
how are alcohols dehydrated to alkenes
using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
42
how are alcohols oxidised to form aldehydes then carboxylic acids / ketones
using acidified permanganate, acidified | dichromate or hot copper(II) oxide
43
what does an alkoxide contain
O⁻
44
how are alcohols made into alkoxides
reaction with some reactive metals such as potassium or sodium
45
what catalysts can be used in the formation of ethers from alcohols and carboxylic acids
concentrated sulfuric acid or concentrated phosphoric acid
46
what is the functional group in an acid chloride
COCl (C=O / C-Cl)
47
what catalysts need to be used in the formation of esters from alcohols and acid chlorides?
no catalysts are needed
48
which is a faster reaction, ester formation from alcohol and carboxylic acid, or alcohol and acid chloride
alcohol and acid chloride
49
how is an alkyl group formed from an alkane
one hydrogen is removed
50
what is the general structure for substituted alkane ethers
R' - O - R" where R' and R'' are alkyl groups
51
what can ethers be regarded as
substituted alkanes
52
how is an ether formed
a hydrogen is removed from an alkane, and is replaced with an alkoxy group
53
describe a process in which an ether is produced
the nucleophilic substitution reaction between a monohaloalkane and an alkoxide
54
which ethers are soluble in water
methoxymethane and methoxyethane
55
what type of ethers are insoluble in water and why
large ethers, as they have a large molecular size
56
why are ethers commonly used as solvents
they are relatively inert chemically and will dissolve many organic compounds
57
how can alkenes be prepared
- dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid - base-induced elimination of hydrogen halides from monohaloalkanes
58
what electrophilic addition reactions can alkenes take part in
- 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
what does Markovnikov's rule state
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
which product formed follows Markovnikovs rule
the major product
61
how can carboxylic acids be produced
- 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
reactions of carboxylic acids include:
- 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
how are amines formed
1 or more hydrogen atoms from ammonia are replaced by an alkyl group
64
are amines acidic or basic
basic
65
which amines display hydrogen bonding
primary and secondary
66
are amines strong or weak bases
weak
67
how do amines produce hydroxide ions with water
the nitrogen atom has a lone pair of electrons which can accept a proton from water
68
what is the chemical formula for benzene
C6H6
69
what is the simplest member of the class of aromatic hydrocarbons
benzene
70
why is benzene stable
the delocalisation of electrons in the conjugated system
71
why does benzene not take part in addition reactions
delocalised electrons are present
72
how is a phenyl group formed
one hydrogen atom is substituted for another group in a benzene molecule
73
what is the formula for a phenyl group
-C6H5
74
Benzene rings can take part in electrophilic substitution reactions. Reactions at benzene rings include:
 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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