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Flashcards in SNS - Organic Chemistry - Reactions Deck (176):
1

<p>Synthesis Alkynes Dehalogenation</p>

<p>Basically similar to that for the formation of alkenes. The difference is that the alkane starting material has two halogens on each of the adjacent carbons permitting the formation of two pi bonds</p>

2

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Racemic Mixture</p>

<p>The carbocation can be attacked by a nucleophile from either side. Two stereoisomers can thus be produced causing a racemic mixture</p>

3

<p>Synthesis Alcohols Grignard reagents</p>

<p>Forms an alcohol from an aldehyde or ketone using magnesium bromide in the presence of anhydride and ether </p>

4

<p>Synthesis Carboxylic Acids Oxidation of alkenes </p>

<p>Requires KMnO4 </p>

5

<p>Synthesis 2RCOO -&gt;ThO2, heat-&gt; RCOR + CO2</p>

<p>Synthesis of ketones: Decarboxylation of carboxylic acids</p>

6

<p>Synthesis of alkenes: dehalogenation</p>

<p>Synthesis BrCH2CH2Br + Zn -&gt; CH2CH2 + ZnBr2</p>

7

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols Formation of esters </p>

<p>In the most common method of creating as ester, the alcohol hydroxyl group and the proton from the acid leave and the alkyl group from the alcohol bonds to the resonance-stabilised deprotonated carbonyl group on the acid. The hydroxyl group from the alcohol and the proton from the acid combine to form water and leaving behind an ester</p>

8

<p>In the presence of acids, the hydroxy group is replaced in a substitution reaction or removed in an elimination reaction </p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule</p>

9

<p>Synthesis Alkynes </p>

<p>1. Dehydrohalogenation 2. Dehalogenation</p>

10

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1 vs E2</p>

<p>E2 favours a stronger base and a higher concentration of base</p>

11

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids</p>

<p>1. Nucleophilic Substitution 2. Esterification 3. Formation of anhydrides</p>

12

<p>Requires KMnO4 </p>

<p>Synthesis Carboxylic Acids Oxidation of alkenes </p>

13

Reduction by LiAlH4 or NaBH4

Synthesis

Alcohols

Reduction of aldehydes and ketones

14

<p>Synthesis Ketones</p>

<p>1. Mild oxidation of a secondary alcohol 2. Ozonolysis 3. Decarboxylation of carboxylic acids</p>

15

The reaction of two carboxylic acids

Mechanisms and Reactions Oxygen-Containing Molecules

Carboxylic Acids

Formation of anhydrides

16

<p>If a more stable carbocation can be formed in the transition state, formation will occur via this process </p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Carbocation rearrangement</p>

17

<p>Used to describethe position of the proton in reference to the leaving group Refers to the proton's being on the partially positive end</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2 Antiperiplanar</p>

18

<p>Involves the removal of hydrogen and a halogen from an alkane with a halogen substituent </p>

<p>Synthesis Alkenes Dehydrohalogenation </p>

19

<p>Occurs when adjacent carbons of an alkane are substituted with halogens</p>

<p>Synthesis Alkenes Dehalogenation</p>

20

<p>Synthesis CH3CH2OH -&gt; CH2CH2 + H2O</p>

<p>Synthesis of alkenes: dehydration</p>

21

<p>Two step reaction using Grignard reagents RMgBr</p>

<p>Synthesis Carboxylic Acids Grignard reaction with carbon dioxide </p>

22

<p>Result from the dehydration of two alcohols in the presence of H2SO4 and heat</p>

<p>Synthesis Ethers Dehydration </p>

23

<p>Basically similar to that for the formation of alkenes. The difference is that the alkane starting material has two halogens on each of the adjacent carbons permitting the formation of two pi bonds</p>

<p>Synthesis Alkynes Dehalogenation</p>

24

<p>Synthesis 2CH3-CH2OH -&gt;H2SO4, heat-&gt; CH3-CH2-O-CH2-CH3 + H2O

<p>Synthesis of ethers: Dehydration</p>

25

<p>Synthesis CH2BrCH2Br + 2KOH -&gt; CHCH + 2H2O + 2KBr</p>

<p>Synthesis of alkynes: dehydrohalogenation</p>

26

1. HX addition

2. Radical halogenation

<p>Mechanisms and Reactions Alkenes and Alkynes</p>

27

Mechanisms and Reactions

Alkanes

Nucleophilic Substitution

First order: they depend only on the concentration of the substrate

SN1

28

<p>Synthesis Ketones Decarboxylation of carboxylic acids</p>

<p>Occurs in the presence of ThO2 and heat to form a ketone and carbon dioxide</p>

29

<p>Synthesis R-COH + [O] -&gt;CrO3, H2SO4-&gt; R-COOH</p>

<p>Synthesis of carboxylic acids: Oxidation of primary alcohols</p>

30

<p>Synthesis Ethers</p>

<p>1. Williamson Ether Synthesis 2. Dehydration</p>

31

<p>Synthesis R-CHOH-CHOH-R -&gt;HIO4 -&gt; R-CHO + R-CHO</p>

<p>Synthesis of aldehydes: Oxidation of a Diol</p>

32

CH3-CH=CH2 + H2SO4 + H2O  <->

<-> CH3-CHOH-CH3 + H2SO4

Synthesis of alcohols: Hydration of alkenes

33

<p>reactant. Inversion of configuration occurs with SN2 . The steric hindrance of large groups physically prevents both the leaving grouo and the nucleophile from reacting in one step. Therefore only primary and secondary carbons will react via SN2. Tertiary carbons will react by SN1. SN1s are also more polar and protic, have increased substitution, weak nucleophiles and a low concentration of nucleophiles</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 vs SN2</p>

34

<p>One step bimolecular second order reaction in which the nucleophile attacks the bond of the electronegative leaving group and there is no carbocation formation. Just as the leaving group dissociates, the incoming nucleophile bonds There is no rate determining step</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN2 </p>

35

<p>When an aldehyde and a ketone come together in the presence of a dilute acid or base, the two molecules combine. The products are either hydroxyaldehydes or hydroxyketones</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Aldol Condensation </p>

36

Splitting of a diol (molecule with two hydroxy groups)

Synthesis Aldehydes

Oxidation of a Diol

37

<p>Follows Markovnikov's rule - electrophilic addition of hydrogen to a double bond occurs at the carbon with the greatest number of hydrogens</p>

<p>Synthesis Alcohols Hydration of alkenes </p>

38

<p>A compound that contains a double bond and an alcohol</p>

<p>Enol</p>

39

<p>Synthesis Esters</p>

<p>1. From a carboxylic acid and an alcohol</p>

40

<p>Synthesis of alkenes: dehydration</p>

<p>Synthesis CH3CH2OH -&gt; CH2CH2 + H2O</p>

41

<p>Synthesis of ketones: Mild oxidation of a secondary alcohol</p>

<p>Synthesis CH3-CHOH-CH2-CH3 -&gt;CrO3 + H2SO4-&gt; CH3-CO-CH2-CH3</p>

42

<p>E2 favours heat and bulky bases at higher concentration </p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination SN2 vs E2</p>

43

<p>Mechanisms and Reactions Alkanes Free Radical Halogenation</p>

<p>1. Initiation - formation of a halogen radical - these intiialhalogens are fromed by heat and light in an endothermic process 2. Propagation - chain reaction in which a product and another halogen radical are formed 3. Termination - involves two radicals coming together to form a bond in an exothermic reaction, creating a lower, more stable energy state</p>

44

<p>A tow-step, unimolecular, first-order reaction, First step involves the formation of a carbocation intermediate by the dissociation of a leaving group. The second step involves attack by a nucleophile which becomes the substituted part. The stability of the carbocation determines its reactivity. </p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1</p>

45

R-CH=CH-R + KMnO4 <->

<-> R-CHOH-CHOHR + KMnO4 <-> RCOOH + RCOOH

Synthesis of carboxylic acids: Oxidation of alkenes

46

<p>1. Nucleophilic Substitution 2. Esterification 3. Formation of anhydrides</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids</p>

47

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Carbocation rearrangement</p>

<p>If a more stable carbocation can be formed in the transition state, formation will occur via this process </p>

48

<p>Synthesis Ketones Mild oxidation of a secondary alcohol</p>

<p>Occurs in the presence of CrO3 and H2SO4 to form a ketone and water</p>

49

<p>Used to make longer chains of hydorcarbons The two alkyl groups fro the alkyl bromides are joined and sodium bromide is formed as a side product</p>

<p>Synthesis Alkanes Wurtz reaction</p>

50

CH3-CO-CH3 + LiAlH4 + H+ <->

<-> CH3-COH-CH3

Synthesis of alcohols:

Reduction of aldehydes and ketones

51

<p>In the most common method of creating as ester, the alcohol hydroxyl group and the proton from the acid leave and the alkyl group from the alcohol bonds to the resonance-stabilised deprotonated carbonyl group on the acid. The hydroxyl group from the alcohol and the proton from the acid combine to form water and leaving behind an ester</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols Formation of esters </p>

52

<p>Subject to nucleophillic attack 1. Reactions with Grignard reagents 2. Reactions with alcohols 3. Oxidation 4. Aldol Condensation 5. Keto-Enol Tautomerism</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones</p>

53

<p>Whereas aldehydes and ketones prefer nucleophilic addition reactions, carboxylic acids prefer nucleophilic substitution reactions. </p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids Nucleophilic Substitution</p>

54

1. Dehydrohalogenation

2. Dehydration

3. Dehalogenation

Synthesis Alkenes

55

<p>1. Dehydrohalogenation 2. Dehalogenation</p>

<p>Synthesis Alkynes </p>

56

<p>Occurs in the presence of CrO3 and H2SO4</p>

<p>Synthesis Carboxylic Acids Oxidation of primary alcohols</p>

57

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 vs SN2</p>

<p>One of the easiest ways to determine whether a reactant favours the SN1 or SN2 reaction is to evaluate the bulk of the reactant. Inversion of configuration occurs with SN2 . The steric hindrance of large groups physically prevents both the leaving grouo and the nucleophile from reacting in one step. Therefore only primary and secondary carbons will react via SN2. Tertiary carbons will react by SN1. SN1s are also more polar and protic, have increased substitution, weak nucleophiles and a low concentration of nucleophiles</p>

58

<p>1. Free Radical Halogenation 2. Nucleophilic Substitution and Elimination</p>

<p>Mechanisms and Reactions Alkanes </p>

59

<p>Mechanisms and Reactions Alkenes and Alkynes</p>

<p>The electrons of pi bonds of alkenes and alkynes are responsible for the reactions with other compounds. Generally these molecules react with electron-rich compounds 1. HX addition 2. Radical halogenation</p>

60

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Keto-Enol Tautomerism </p>

<p>Any carbonyl compound with an alpha hydrogen is subject to interconversion between keto and enol forms. This conversion is referred to as tautomerism The keto form is more stable</p>

61

<p>Reaction of a carboxylic acid results in an ester and water</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids Esterification</p>

62

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Oxidation </p>

<p>The oxidation of aldehydes involves two common reagents - Tollen's and Benedict's. Since whenever there is oxidation there is reduction, Tollen's reagent forms silver metal from the reduction of a silver salt in the presence of an aldehyde only (called the silver mirror test)</p>

63

<p>Occurs in the presence of CrO3 and H2SO4 to form a ketone and water</p>

<p>Synthesis Ketones Mild oxidation of a secondary alcohol</p>

64

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Aldol Condensation </p>

<p>When an aldehyde and a ketone come together in the presence of a dilute acid or base, the two molecules combine. The products are either hydroxyaldehydes or hydroxyketones</p>

65

<p>Synthesis of Alkanes: Wurtz reaction</p>

<p>Synthesis 2RBr + 2Na -&gt; RR + 2NaBr</p>

66

<p>The starting material can be linear or cyclic. Depending on the substitution of the double bond, an aldehyde or ketone is formed Occurs in the presence of O3, Zn and H2O</p>

<p>Synthesis Ketones Ozonolysis </p>

67

<p>Synthesis of ketones: Decarboxylation of carboxylic acids</p>

<p>Synthesis 2RCOO -&gt;ThO2, heat-&gt; RCOR + CO2</p>

68

<p>Synthesis Aldehydes Oxidation of a Diol</p>

<p>Thge formation of two aldehydes results from the splitting of a diol (molecule with two hydroxy groups)</p>

69

<p>Markovnikov's rule states that the electrophillic addition of a hydrogen to a double bond will occur at th carbon which has the greatest number of hydrogens, Stability of the carbocation intermediate dictates the placement of substituents in this addition reaction</p>

<p>Mechanisms and Reactions Alkenes and Alkynes HX Addition</p>

70

<p>Synthesis Aldehydes</p>

<p>1. Mild oxidation of a Primary Alcohol 2. Oxidation of a Diol</p>

71

<p>Synthesis of carboxylic acids: Grignard reaction with carbon dioxide</p>

<p>Synthesis RMgBr + CO2 -&gt; R-CO-OMgBr -&gt;H+-&gt; R-COOH + MgBr</p>

72

<p>E1 favours higher temperatures</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination SN1 vs E1</p>

73

<p>1. Mild oxidation of a secondary alcohol 2. Ozonolysis 3. Decarboxylation of carboxylic acids</p>

<p>Synthesis Ketones</p>

74

<p>When the electrophilic carbon is attacked by an alcohol, the aldehyde or ketone undergoes a nucleophilic addition reaction and adds to the carbonyl group When one alcohol reacts, the result is either the formation of a hemiacetal from an aldehyde or the formation of a hemiaketal from a ketone. When a second molecule reacts, the hemiacetal and hemiketal form the acetal and ketal respectively</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Reactions with alcohols </p>

75

<p>Synthesis Alcohols</p>

<p>1. Hydration of alkenes 2. Grignard reagents 3. Reduction of aldehydes and ketones</p>

76

<p>Two-step, bimolecular, second order reaction. More effective elimination reaction than E1 Because of steric hindrance, E2 reactions don't occur with bulky groups. No rearrangement occurs</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2</p>

77

<p>Synthesis Aldehydes Mild oxidation of a Primary Alcohol </p>

<p>In the presence of heat and an oxidising agent, to form an aldehyde and water</p>

78

<p>Synthesis Alkanes</p>

<p>1. Wurtz reaction</p>

79

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Reactions with alcohols </p>

<p>When the electrophilic carbon is attacked by an alcohol, the aldehyde or ketone undergoes a nucleophilic addition reaction and adds to the carbonyl group When one alcohol reacts, the result is either the formation of a hemiacetal from an aldehyde or the formation of a hemiaketal from a ketone. When a second molecule reacts, the hemiacetal and hemiketal form the acetal and ketal respectively</p>

80

CH3CH2Br +KOH <->

<-> CH2=CH2 + H2O + KBr

Synthesis of alkenes: dehydrohalogenation

81

<p>Synthesis Carboxylic Acids Grignard reaction with carbon dioxide </p>

<p>Two step reaction using Grignard reagents RMgBr</p>

82

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols Dehydration to alkenes</p>

<p>One method of creating alkenes. The hydroxy group and a hydrogen leave in an elimination reaction, producing water and an alkene in the presence of heat and H2SO4</p>

83

<p>Synthesis of ethers: Dehydration</p>

<p>Synthesis 2CH3-CH2OH -&gt;H2SO4, heat-&gt; CH3-CH2-O-CH2-CH3 + H2O

84

<p>The formation of the carbocation. The E1 rate is determined by the substrate concentration</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1 Rate Determining Step</p>

85

Synthesis of alcohols: Grignard reagents

RMgBr + HCHO + Anhydride/Ether <-> RCH2OMgBr + H+ <-> RCH2OH + MgBr

86

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1</p>

<p>A tow-step, unimolecular, first-order reaction, First step involves the formation of a carbocation intermediate by the dissociation of a leaving group. The second step involves attack by a nucleophile which becomes the substituted part. The stability of the carbocation determines its reactivity. </p>

87

<p>E2 favours a stronger base and a higher concentration of base</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1 vs E2</p>

88

<p>Synthesis Alcohols Hydration of alkenes </p>

<p>Follows Markovnikov's rule - electrophilic addition of hydrogen to a double bond occurs at the carbon with the greatest number of hydrogens</p>

89

<p>Favours aprotic solvents - free of protons for hydrogen bonding</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN2 Conditions</p>

90

<p>Synthesis Ketones Ozonolysis </p>

<p>The starting material can be linear or cyclic. Depending on the substitution of the double bond, an aldehyde or ketone is formed Occurs in the presence of O3, Zn and H2O</p>

91

A weak oxidising agent, such as pyridinium chlorochromate (PCC)

Mechanisms and Reactions

Oxygen-Containing Molecule

Alcohols: Oxidation to aldehydes

92

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids Esterification</p>

<p>Reaction of a carboxylic acid results in an ester and water</p>

93

<p>The lone pair of electrons in an amine make this compound act as a nucleophile. Ammonia and primary amines are the best nucleophiles - in more substituted amines, the electrons aren't able to react with incoming electrophiles due to steric hindrances. Amines react with electrophiles and carbonyls to form imines and amides respectively</p>

<p>Mechanisms and Reactions Amines</p>

94

<p>Mechanisms and Reactions Alkenes and Alkynes Radical Halogenation</p>

<p>In an anti-Markovnikov reaction, a radical halogen first bonds to the lesser substituted carbon of the alkene. The resulting radical reacts with the hydrogen of a hydrogen halide forming an anti-Markovnikov product and another halogen radical</p>

95

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Reactions with Grignard reagents</p>

<p>Grignards are alkylmagnesium halides with the general formula RMgX When they come into contact with aldehydes and ketones, addition reactions occur which result in the formation of a number of alcohols</p>

96

<p>Synthesis Alkenes Dehalogenation</p>

<p>Occurs when adjacent carbons of an alkane are substituted with halogens</p>

97

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1 Rate Determining Step</p>

<p>The formation of the carbocation. The E1 rate is determined by the substrate concentration</p>

98

<p>Synthesis of alcohols: Reduction of aldehydes and ketones</p>

<p>CH3-CO-CH3 + LiAlH4 + H+ -&gt; CH3-COH-CH3</p>

99

<p>Synthesis of carboxylic acids: Oxidation of alkenes</p>

<p>Synthesis R-CH=CH-R + KMnO4 -&gt; R-CHOH-CHOHR -&gt;KMnO4-&gt; RCOOH + RCOOH</p>

100

<p>Synthesis RMgBr + CO2 -&gt; R-CO-OMgBr -&gt;H+-&gt; R-COOH + MgBr</p>

<p>Synthesis of carboxylic acids: Grignard reaction with carbon dioxide</p>

101

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Conditions</p>

<p>1. This reaction prefers bulky electrophiles 3⁰ &amp;lt; 2⁰ &amp;lt; 1⁰ 2. Favours protic solvents - protons readily available for hydrogen bonding</p>

102

<p>Requires NaOH. Forms an alcohol and a carboxylic acid</p>

<p>Synthesis Carboxylic Acids Saponification of esters </p>

103

<p>Synthesis of carboxylic acids: Saponification of esters</p>

<p>Synthesis R-CO-O-R + NaOH R-CO-O-Na + R-OH -&gt;H+-&gt; R-COOH</p>

104

<p>Synthesis Ethers Williamson Ether Synthesis</p>

<p>The reaction between an alcohol and a strong base results in the formation of an alkoxide that reacts via an SN2 process to form an ether</p>

105

<p>Mechanisms and Reactions Alkanes </p>

<p>1. Free Radical Halogenation 2. Nucleophilic Substitution and Elimination</p>

106

<p>Basically similar to that for the formation of alkenes. The difference is that there is more KOH to remove the alkene hydrogens to form the second pi bond of the alkyne</p>

<p>Synthesis Alkynes Dehydrohalogenation </p>

107

<p>1. Williamson Ether Synthesis 2. Dehydration</p>

<p>Synthesis Ethers</p>

108

<p>Mechanisms and Reactions Amines</p>

<p>The lone pair of electrons in an amine make this compound act as a nucleophile. Ammonia and primary amines are the best nucleophiles - in more substituted amines, the electrons aren't able to react with incoming electrophiles due to steric hindrances. Amines react with electrophiles and carbonyls to form imines and amides respectively</p>

109

<p>Synthesis Alcohols Reduction of aldehydes and ketones</p>

<p>Easily accomplished by the reduction of a carbonyl compound by LiAlH4 or NaBH4. Ketones reduce to secondary alcohols, whilst aldehydes reduce to primary alcohols Milder reducing agents can reduce carboxylic acids to aldehydes but not alcohols</p>

110

<p>Synthesis Carboxylic Acids Oxidation of primary alcohols</p>

<p>Occurs in the presence of CrO3 and H2SO4</p>

111

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2 Antiperiplanar</p>

<p>Used to describethe position of the proton in reference to the leaving group Refers to the proton's being on the partially positive end</p>

112

<p>Mechanisms and Reactions Alkenes and Alkynes HX Addition</p>

<p>Markovnikov's rule states that the electrophillic addition of a hydrogen to a double bond will occur at th carbon which has the greatest number of hydrogens, Stability of the carbocation intermediate dictates the placement of substituents in this addition reaction</p>

113

<p>Occurs in the presence of ThO2 and heat to form a ketone and carbon dioxide</p>

<p>Synthesis Ketones Decarboxylation of carboxylic acids</p>

114

<p>1. Hydration of alkenes 2. Grignard reagents 3. Reduction of aldehydes and ketones</p>

<p>Synthesis Alcohols</p>

115

<p>1. Oxidation to aldehydes 2. Dehydration to alkenes 3. Formation of esters with carboxylic acids</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols</p>

116

<p>Synthesis Carboxylic Acids</p>

<p>1. Oxidation of alkenes 2. Grignard reaction with carbon dioxide 3. Oxidation of primary alcohols 4. Saponification of esters</p>

117

<p>In the presence of heat and an oxidising agent, to form an aldehyde and water</p>

<p>Synthesis Aldehydes Mild oxidation of a Primary Alcohol </p>

118

<p>Grignards are alkylmagnesium halides with the general formula RMgX When they come into contact with aldehydes and ketones, addition reactions occur which result in the formation of a number of alcohols</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Reactions with Grignard reagents</p>

119

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2</p>

<p>Two-step, bimolecular, second order reaction. More effective elimination reaction than E1 Because of steric hindrance, E2 reactions don't occur with bulky groups. No rearrangement occurs</p>

120

<p>Synthesis of alcohols: Hydration of alkenes</p>

<p>CH3-CH=CH2 + H2SO4 + H2O -&gt; CH3-CHOH-CH3 + H2SO4 </p>

121

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN2 </p>

<p>One step bimolecular second order reaction in which the nucleophile attacks the bond of the electronegative leaving group and there is no carbocation formation. Just as the leaving group dissociates, the incoming nucleophile bonds There is no rate determining step</p>

122

<p>Two-step unimolecular first order reaction. The first step is dissociation of the leaving group forming a carbocation. Rather than nucleophillic addition, however, the carbocation loses a proton to the nucleophile (strong base). The most substituted double bond forms, trans preferably.</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1</p>

123

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids Nucleophilic Substitution</p>

<p>Whereas aldehydes and ketones prefer nucleophilic addition reactions, carboxylic acids prefer nucleophilic substitution reactions. </p>

124

<p>Synthesis CH3-CHOH-CH2-CH3 -&gt;CrO3 + H2SO4-&gt; CH3-CO-CH2-CH3</p>

<p>Synthesis of ketones: Mild oxidation of a secondary alcohol</p>

125

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination SN1 vs E1</p>

<p>E1 favours higher temperatures</p>

126

<p>Synthesis Alkenes </p>

<p>The substitution of the alkane starting material dictates which method is used to create the pi bond ppresent in alkenes. All three methods are elimination reactions 1. Dehydrohalogenation 2. Dehydration 3. Dehalogenation</p>

127

<p> Mechanisms and Reactions Structure and Stability of Radicals</p>

<p> In general, the more substituted a radical, the more stable it is</p>

128

<p>Synthesis of alkenes: dehydrohalogenation</p>

<p>Synthesis CH3CH2Br +KOH -&gt; CH2=CH2 + H2O + KBr</p>

129

<p>Synthesis of aldehydes: Mild oxidation of a Primary Alcohol</p>

<p>Synthesis RCH2OH + [O] -&gt;heat-&gt; RCHO + H2O</p>

130

<p>A hydroxy and a hydrogen are removed forming an alkene and water. The starting material is an alcohol</p>

<p>Synthesis Alkenes Dehydration </p>

131

<p> In general, the more substituted a radical, the more stable it is</p>

<p> Mechanisms and Reactions Structure and Stability of Radicals</p>

132

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination SN2 vs E2</p>

<p>E2 favours heat and bulky bases at higher concentration </p>

133

<p>Synthesis Carboxylic Acids Saponification of esters </p>

<p>Requires NaOH. Forms an alcohol and a carboxylic acid</p>

134

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols Oxidation to aldehydes</p>

<p>With a weak oxidising agent, such as pyridinium chlorochromate (PCC), a primary alcohol can be oxidised to an aldehyde. With further oxidation, the alcohol will continue to react until a carboxylic acid is formed</p>

135

<p>Synthesis of alkynes: dehydrohalogenation</p>

<p>Synthesis CH2BrCH2Br + 2KOH -&gt; CHCH + 2H2O + 2KBr</p>

136

<p>1. This reaction prefers bulky electrophiles 3⁰ &amp;lt; 2⁰ &amp;lt; 1⁰ 2. Favours protic solvents - protons readily available for hydrogen bonding</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Conditions</p>

137

<p>The oxidation of aldehydes involves two common reagents - Tollen's and Benedict's. Since whenever there is oxidation there is reduction, Tollen's reagent forms silver metal from the reduction of a silver salt in the presence of an aldehyde only (called the silver mirror test)</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Oxidation </p>

138

<p>Synthesis of aldehydes: Oxidation of a Diol</p>

<p>Synthesis R-CHOH-CHOH-R -&gt;HIO4 -&gt; R-CHO + R-CHO</p>

139

<p>Mechanisms and Reactions Oxygen-Containing Molecule</p>

<p>In the presence of acids, the hydroxy group is replaced in a substitution reaction or removed in an elimination reaction </p>

140

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN2 Conditions</p>

<p>Favours aprotic solvents - free of protons for hydrogen bonding</p>

141

<p>Synthesis Alkenes Dehydration </p>

<p>A hydroxy and a hydrogen are removed forming an alkene and water. The starting material is an alcohol</p>

142

<p>1. Initiation - formation of a halogen radical - these intiialhalogens are fromed by heat and light in an endothermic process 2. Propagation - chain reaction in which a product and another halogen radical are formed 3. Termination - involves two radicals coming together to form a bond in an exothermic reaction, creating a lower, more stable energy state</p>

<p>Mechanisms and Reactions Alkanes Free Radical Halogenation</p>

143

<p>Synthesis RCH2OH + [O] -&gt;heat-&gt; RCHO + H2O</p>

<p>Synthesis of aldehydes: Mild oxidation of a Primary Alcohol</p>

144

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution and Elimination</p>

<p>Four types of reactions may occur when elecron-rich and electron-deficient compounds come into contact. The first two result in substitution on alkanes whereas the second two result in elimination and the formation of alkenes</p>

145

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E1</p>

<p>Two-step unimolecular first order reaction. The first step is dissociation of the leaving group forming a carbocation. Rather than nucleophillic addition, however, the carbocation loses a proton to the nucleophile (strong base). The most substituted double bond forms, trans preferably.</p>

146

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones</p>

<p>Subject to nucleophillic attack 1. Reactions with Grignard reagents 2. Reactions with alcohols 3. Oxidation 4. Aldol Condensation 5. Keto-Enol Tautomerism</p>

147

<p>Synthesis Alkanes Wurtz reaction</p>

<p>Used to make longer chains of hydorcarbons The two alkyl groups fro the alkyl bromides are joined and sodium bromide is formed as a side product</p>

148

<p>Any carbonyl compound with an alpha hydrogen is subject to interconversion between keto and enol forms. This conversion is referred to as tautomerism The keto form is more stable</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Aldehydes and Ketones Keto-Enol Tautomerism </p>

149

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2 Rate Determining Step</p>

<p>Determined by concentrations of both the nucleophile/base and the substrate</p>

150

<p>Forms an alcohol from an aldehyde or ketone using magnesium bromide in the presence of anhydride and ether </p>

<p>Synthesis Alcohols Grignard reagents</p>

151

<p>Synthesis of alkynes: dehalogenation</p>

<p>CHBr2CHBr2 + 2Zn -&gt; CHCH + 2ZnBr2</p>

152

<p>1. Oxidation of alkenes 2. Grignard reaction with carbon dioxide 3. Oxidation of primary alcohols 4. Saponification of esters</p>

<p>Synthesis Carboxylic Acids</p>

153

<p>1. Mild oxidation of a Primary Alcohol 2. Oxidation of a Diol</p>

<p>Synthesis Aldehydes</p>

154

<p>Synthesis BrCH2CH2Br + Zn -&gt; CH2CH2 + ZnBr2</p>

<p>Synthesis of alkenes: dehalogenation</p>

155

<p>There are three reactions to note: 1. Glycoside formation - non-reducing sugars, acetals that don't undergo mutorotation 2. Ether formation 3. Ester formation</p>

<p>Mechanisms and Reactions Carbohydrates</p>

156

<p>In an anti-Markovnikov reaction, a radical halogen first bonds to the lesser substituted carbon of the alkene. The resulting radical reacts with the hydrogen of a hydrogen halide forming an anti-Markovnikov product and another halogen radical</p>

<p>Mechanisms and Reactions Alkenes and Alkynes Radical Halogenation</p>

157

<p>Synthesis of carboxylic acids: Oxidation of primary alcohols</p>

<p>Synthesis R-COH + [O] -&gt;CrO3, H2SO4-&gt; R-COOH</p>

158

<p>1. Wurtz reaction</p>

<p>Synthesis Alkanes</p>

159

<p>CHBr2CHBr2 + 2Zn -&gt; CHCH + 2ZnBr2</p>

<p>Synthesis of alkynes: dehalogenation</p>

160

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Reaction Order</p>

<p>SN1 reactions are first order: they depend only on the concentration of the substrate</p>

161

<p>Determined by concentrations of both the nucleophile/base and the substrate</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Elimination E2 Rate Determining Step</p>

162

<p>Synthesis Ethers Dehydration </p>

<p>Result from the dehydration of two alcohols in the presence of H2SO4 and heat</p>

163

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols</p>

<p>1. Oxidation to aldehydes 2. Dehydration to alkenes 3. Formation of esters with carboxylic acids</p>

164

<p>Synthesis 2RBr + 2Na -&gt; RR + 2NaBr</p>

<p>Synthesis of Alkanes: Wurtz reaction</p>

165

<p>Four types of reactions may occur when elecron-rich and electron-deficient compounds come into contact. The first two result in substitution on alkanes whereas the second two result in elimination and the formation of alkenes</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution and Elimination</p>

166

<p>Mechanisms and Reactions Oxygen-Containing Molecule Carboxylic Acids Formation of anhydrides</p>

<p>The reaction of two carboxylic acids results in the formation of a special type of molecule known as an anhydride</p>

167

<p>The carbocation can be attacked by a nucleophile from either side. Two stereoisomers can thus be produced causing a racemic mixture</p>

<p>Mechanisms and Reactions Alkanes Nucleophilic Substitution SN1 Racemic Mixture</p>

168

<p>1. From a carboxylic acid and an alcohol</p>

<p>Synthesis Esters</p>

169

<p>Synthesis R-CO-O-R + NaOH R-CO-O-Na + R-OH -&gt;H+-&gt; R-COOH</p>

<p>Synthesis of carboxylic acids: Saponification of esters</p>

170

<p>Synthesis Alkynes Dehydrohalogenation </p>

<p>Basically similar to that for the formation of alkenes. The difference is that there is more KOH to remove the alkene hydrogens to form the second pi bond of the alkyne</p>

171

<p>One method of creating alkenes. The hydroxy group and a hydrogen leave in an elimination reaction, producing water and an alkene in the presence of heat and H2SO4</p>

<p>Mechanisms and Reactions Oxygen-Containing Molecule Alcohols Dehydration to alkenes</p>

172

<p>Mechanisms and Reactions Carbohydrates</p>

<p>There are three reactions to note: 1. Glycoside formation - non-reducing sugars, acetals that don't undergo mutorotation 2. Ether formation 3. Ester formation</p>

173

<p>Synthesis RMgBr + HCHO -&gt; Anhydride/Ether -&gt; RCH2OMgBr -&gt; H+ -&gt; RCH2OH + MgBr</p>

<p>Synthesis of alcohols: Grignard reagents</p>

174

<p>Enol</p>

<p>A compound that contains a double bond and an alcohol</p>

175

<p>The reaction between an alcohol and a strong base results in the formation of an alkoxide that reacts via an SN2 process to form an ether</p>

<p>Synthesis Ethers Williamson Ether Synthesis</p>

176

<p>Synthesis Alkenes Dehydrohalogenation </p>

<p>Involves the removal of hydrogen and a halogen from an alkane with a halogen substituent </p>

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