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CHEM > 2.2 Synthesis > Flashcards

2.2 Synthesis Flashcards

1
Q

types of bond fission

A
  • homolytic
  • heterolytic
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2
Q
  • homolytic
  • heterolytic
A

types of bond fission

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3
Q

bond fission

A

bond breaking

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4
Q

homolytic fission

A
  • results in the formation of two neutral radicals
  • occurs when each atom retains one electron from the sigma covalent bond and the bond
    breaks evenly
  • normally occurs when non-polar covalent bonds are broken
  • tend to result in the formation of very complex mixtures of products, making them unsuitable for organic synthesis
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5
Q
  • results in the formation of two neutral radicals
  • occurs when each atom retains one electron from the sigma covalent bond and the bond
    breaks evenly
  • normally occurs when non-polar covalent bonds are broken
  • usually to result in the formation of very complex mixtures of products, making them unsuitable for organic synthesis
A

homolytic fission

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6
Q

heterolytic fission

A
  • results in the formation of two oppositely charged ions
  • occurs when one atom retains both electrons from the σ covalent bond and the bond breaks unevenly
  • normally occurs when polar covalent bonds are broken
  • usually result in far fewer products than reactions involving homolytic fission, and so are better suited for organic synthesis
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7
Q
  • results in the formation of two oppositely charged ions
  • occurs when one atom retains both electrons from the σ covalent bond and the bond breaks unevenly
  • normally occurs when polar covalent bonds are broken
  • usually result in far fewer products than reactions involving homolytic fission, and so are better suited for organic synthesis
A

heterolytic fission

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8
Q

what are attacking groups classified as in reactions involving heterolytic bond fission

A
  • nucleophiles
  • electrophiles
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9
Q

when are groups classified as nucleophiles or electrophiles

A

if they are an attacking group in heterolytic bond fission

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10
Q

nucleophile

A
  • negatively charged ions or neutral molecules that are electron rich, such as
    Cl−, Br−, OH−, CN− , NH3 and H2O
  • attracted towards atoms bearing a partial (δ+) or full positive charge
  • capable of donating an electron pair to form a new covalent bond
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11
Q
  • negatively charged ions or neutral molecules that are electron rich, such as
    Cl−, Br−, OH−, CN− , NH3 and H2O
  • attracted towards atoms bearing a partial (δ+) or full positive charge
  • capable of donating an electron pair to form a new covalent bond
A

nucleophiles

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12
Q

electrophile

A
  • positively charged ions or neutral molecules that are electron deficient, such as H+,NO2+ and SO3
  • attracted towards atoms bearing a partial (δ−) or full negative charge
  • capable of accepting an electron pair to form a new covalent bond
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13
Q
  • positively charged ions or neutral molecules that are electron deficient, such as H+,NO2+ and SO3
  • attracted towards atoms bearing a partial (δ−) or full negative charge
  • capable of accepting an electron pair to form a new covalent bond
A

electrophile

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14
Q

haloalkane

A
  • aka alkyl halides
  • substituted alkanes in which one or more of the H atoms is replaced with a halogen atom
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15
Q
  • aka alkyl halides
  • substituted alkanes in which one or more of the H atoms is replaced with a halogen atom
A

haloalkane

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16
Q

monohaloalkane

A
  • contain only one halogen atom
  • can be classified as primary, secondary or tertiary according to the number of alkyl groups attached to the carbon atom containing the halogen atom
  • take part in elimination reactions to form alkenes using a strong base, such as potassium or sodium hydroxide in ethanol
  • take part in nucleophilic substitution reactions with:
    — aqueous alkalis to form alcohols
    — alcoholic alkoxides to form ethers
    — ethanolic cyanide to form nitriles (chain length increased by one carbon atom) that can be hydrolysed to carboxylic acids
  • can take part in nucleophilic substitution by one of two mechanisms: sn1 or sn2
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17
Q

mechanisms for monoalkanes in nucleophilic substitution

A
  • sn1: nucleophilic substitution reaction with one species in the rate determining step and occurs in a minimum of two steps via a trigonal planar carbocation intermediate
  • sn2: nucleophilic substitution reaction with two species in the rate determining step and occurs in a single step via a single five-centred, trigonal bipyramidal transition state
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18
Q
  • sn1: nucleophilic substitution reaction with one species in the rate determining step and occurs in a minimum of two steps via a trigonal planar carbocation intermediate
  • sn2: nucleophilic substitution reaction with two species in the rate determining step and occurs in a single step via a single five-centred, trigonal bipyramidal transition state
A

mechanisms for monoalkanes in nucleophilic substitution

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19
Q

alcohol

A

substituted alkanes in which one or more of the hydrogen atoms is replaced with a hydroxyl group, OH-

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20
Q

substituted alkanes in which one or more of the hydrogen atoms is replaced with a hydroxyl group, OH-

A

alcohol

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21
Q

what can alcohols be prepared from

A
  • haloalkanes by substitution
  • alkenes by acid-catalysed hydration (addition)
  • aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride
22
Q

what can be prepared from the following
- haloalkanes by substitution
- alkenes by acid-catalysed hydration (addition)
- aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride

23
Q

reactions of alcohols

A
  • dehydration to form alkenes using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
  • oxidation of primary alcohols to form aldehydes and then carboxylic acids and secondary alcohols to form ketones, using acidified permanganate, acidified dichromate or hot copper(II) oxide
  • formation of alcoholic alkoxides by reaction with some reactive metals such as potassium or sodium, which can then be reacted with monohaloalkanes to form ethers
  • formation of esters by reaction with carboxylic acids using concentrated sulfuric acid or concentrated phosphoric acid as a catalyst
  • formation of esters by reaction with acid chlorides ( R-COCl) — this gives a faster reaction than reaction with carboxylic acids, and no catalyst is needed
24
Q
  • dehydration to form alkenes using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
  • oxidation of primary alcohols to form aldehydes and then carboxylic acids and secondary alcohols to form ketones, using acidified permanganate, acidified dichromate or hot copper(II) oxide
  • formation of alcoholic alkoxides by reaction with some reactive metals such as potassium or sodium, which can then be reacted with monohaloalkanes to form ethers
  • formation of esters by reaction with carboxylic acids using concentrated sulfuric acid or concentrated phosphoric acid as a catalyst
  • formation of esters by reaction with acid chlorides ( R-COCl) — this gives a faster reaction than reaction with carboxylic acids, and no catalyst is needed
A

reactions of alcohols

25
Q

hydroxyl group and polarity

A
  • hydroyl groups make alcohol polar
  • this gives rise to hydrogen bonding
  • hydrogen bonding can be used to explain the properties of alcohols, including BP, MP, viscosity, and solubility in water
26
Q

ethers

A

substituted alkanes in which a hydrogen atom is replaced with an alkoxy functional group, -OR, and have the general structure R’-O-R’’, where R’ and R’’ are alkyl groups

27
Q

substituted alkanes in which a hydrogen atom is replaced with an alkoxy functional group, -OR, and have the general structure R’-O-R’’, where R’ and R’’ are alkyl groups

28
Q

what can ethers be prepared from

A

nucleophilic substitution reaction by reacting a monohaloalkane with an alkoxide

29
Q

what is prepared from a nucleophilic substitution reaction by reacting a monohaloalkane with an alkoxide

30
Q

ethers and isomeric alcohols BP

A
  • ethers have lower BPs than isomeric alcohols
  • this is due to the lack of hydrogen bonding
31
Q

solubility of ethers in water

A
  • methoxymethane and methoxyethane are soluble in water
  • larger ethers are insoluble in water due to their increased molecular size
32
Q

ethers use

A

commonly used as solvents since they are relatively inert chemically and will dissolve many organic compounds

33
Q

what are commonly used as solvents since they are relatively inert chemically and will dissolve many organic compounds

34
Q

how to prepare alkenes

A
  • dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
  • base-induced elimination of hydrogen halides from monohaloalkanes
35
Q

what can be prepared from:
- dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid

  • base-induced elimination of hydrogen halides from monohaloalkanes
36
Q

alkene reactions

A
  • hydrogen to form alkanes in the presence of a catalyst
  • halogens to form dihaloalkanes
  • hydrogen halides to form monohaloalkanes
  • water using an acid catalyst to form alcohols
37
Q
  • hydrogen to form alkanes in the presence of a catalyst
  • halogens to form dihaloalkanes
  • hydrogen halides to form monohaloalkanes
  • water using an acid catalyst to form alcohols
A

alkene reactions

38
Q

Markovnikov’s rule

A
  • 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 attached to it already
  • this rule can be used to predict major and minor products formed during the reaction of a hydrogen halide or water with alkenes
39
Q
  • 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 attached to it already
  • this rule can be used to predict major and minor products formed during the reaction of a hydrogen halide or water with alkenes
A

Markovnikov’s rule

40
Q

how to prepare carboxylic acid

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
41
Q

what can be prepared from he following:
- 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
A

carboxylic acid

42
Q

reactions of carboxylic acids

A
  • formation of salts by reactions with metals or bases
  • condensation reactions with alcohols to form esters in the presence of concentrated sulfuric or concentrated phosphoric acid
  • reaction with amines to form alkylammonium salts that form amides when heated
  • reduction with lithium aluminium hydride to form primary alcohols
43
Q
  • formation of salts by reactions with metals or bases
  • condensation reactions with alcohols to form esters in the presence of concentrated sulfuric or concentrated phosphoric acid
  • reaction with amines to form alkylammonium salts that form amides when heated
  • reduction with lithium aluminium hydride to form primary alcohols
A

reactions of carboxylic acids

44
Q

amine

A
  • organic derivative of ammonia in which one or more hydrogen atoms of ammonia has been replaced by an alkyl group
  • can be classified as primary, secondary, or tertiary, according to the number of alkyl groups attached to the nitrogen atom
45
Q
  • organic derivative of ammonia in which one or more hydrogen atoms of ammonia has been replaced by an alkyl group
  • can be classified as primary, secondary, or tertiary, according to the number of alkyl groups attached to the nitrogen atom
46
Q

amine reaction

A

reacts with acids to from salts

47
Q

what reacts with acids to from salts

48
Q

amines solubility in water

A
  • primary, secondary and tertiary amine molecules can hydrogen-bond with water molecules
  • this explains the appreciable solubility of the shorter chain length amines in water
49
Q
  • primary, secondary and tertiary amine molecules can hydrogen-bond with water molecules
  • this explains the appreciable solubility of the shorter chain length amines in water
A

amines solubility in water

51
Q

carbocation

CHEM (10 decks)

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