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CHM2911 > Organic Chemistry II > Flashcards

Organic Chemistry II Flashcards

1
Q

Define

Acetal

A

an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule

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2
Q

Define

Acyl

A

denoting a radical of general formula —C(O)R, where R is an alkyl group, derived from a carboxylic acid

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3
Q

Define

Aldol condensation

A

a condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by dehydration to give a conjugated enone

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4
Q

Define

Aldol reaction

A

When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone

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5
Q

Define

Bond hybridisation

A

the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory

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6
Q

Define

Carbonyl

A

of or denoting the divalent radical =C=O, present in such organic compounds as aldehydes, ketones, amides, and esters, and in organic acids as part of the carboxyl group

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7
Q

Define

Chemoselectivity

A

the selective reactivity of one functional group in the presence of others; often this process in convoluted and protecting groups are on the molecular connectivity alone

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8
Q

Define

Claisen ester condensation

A

a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone

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9
Q

Define

Claisen rearrangement

A

a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen

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10
Q

Define

Conjugation

A

a system of connected p orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability

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11
Q

Define

Cope rearrangement

A

the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene

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12
Q

Define

Cycloaddition reactions

A

a chemical reaction, in which “two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity.”

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13
Q

Define

De-shielded

A

A nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects

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14
Q

Define

Diels-Alder reaction

A

an addition reaction in which a conjugated diene reacts with a compound with a double or triple bond so as to form a six-membered ring

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15
Q

Definition

an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule

A

Acetal

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16
Q

Definition

denoting a radical of general formula —C(O)R, where R is an alkyl group, derived from a carboxylic acid

A

Acyl

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17
Q

Definition

a condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by dehydration to give a conjugated enone

A

Aldol condensation

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18
Q

Definition

When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone

A

Aldol reaction

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19
Q

Definition

the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory

A

Bond hybridisation

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20
Q

Definition

of or denoting the divalent radical =C=O, present in such organic compounds as aldehydes, ketones, amides, and esters, and in organic acids as part of the carboxyl group

A

Carbonyl

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21
Q

Definition

the selective reactivity of one functional group in the presence of others; often this process in convoluted and protecting groups are on the molecular connectivity alone

A

Chemoselectivity

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22
Q

Definition

a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone

A

Claisen ester condensation

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23
Q

Definition

a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen

A

Claisen rearrangement

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24
Q

Definition

a system of connected p orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability

A

Conjugation

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25
Q

Definition

the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene

A

Cope rearrangement

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26
Q

Definition

a chemical reaction, in which “two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity.”

A

Cycloaddition reactions

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27
Q

Definition

A nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects

A

De-shielded

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28
Q

Definition

an addition reaction in which a conjugated diene reacts with a compound with a double or triple bond so as to form a six-membered ring

A

Diels-Alder reaction

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29
Q

Define

Electron delocalisation

A

electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond

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30
Q

Define

Electrophilic aromatic substitution

A

an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile

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31
Q

Define

Electrophilicity

A

The property of being electrophilic

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32
Q

Define

Enamines

A

an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine

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33
Q

Define

Enol

A

an organic compound that contains a hydroxyl group bonded to a carbon atom having a double bond and that is usually characterized by the grouping C=C(OH)

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34
Q

Define

Enolate

A

Salts of enols (or of the tautomeric aldehydes or ketones), in which the anionic charge is delocalized over oxygen and carbon, or similar covalent metal derivatives in which the metal is bound to oxygen

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35
Q
A
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36
Q

Define

Fischer esterification

A

the esterification of a Carboxylic acid by heating it with an alcohol in the presence of a strong acid as the catalyst

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37
Q

Define

Grignard reaction

A

an organometallic chemical reaction in which alkyl, vinyl, or aryl-magnesium halides (Grignard reagent) add to a carbonyl group in an aldehyde or ketone

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38
Q

Define

Heteroatom

A

any atom that is not carbon or hydrogen

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39
Q

Define

Hydrate

A

a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element

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40
Q

Define

Hydride shift

A

a carbocation rearrangement in which a hydrogen atom in a carbocation migrates to the carbon atom bearing the formal charge of +1 (carbon 2) from an adjacent carbon (carbon 1)

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41
Q

Define

Imine

A

a functional group or chemical compound containing a carbon–nitrogen double bond

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42
Q

Define

Keto-enol tautomerisation

A

a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol (an alcohol). The keto and enol forms are said to be tautomers of each other.

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43
Q

Define

Leaving group

A

a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.

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44
Q

Define

Nucleophile

A
  • a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
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45
Q

Define

Nucleophilic acyl addition

A

a class of substitution reactions involving nucleophiles andacyl compounds. In this type of reaction, a nucleophile – such as an alcohol, amine, or enolate – displaces the leaving group of an acyl derivative – such as an acid halide, anhydride, or ester

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46
Q

Define

Oxidation

A

a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen

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47
Q

Define

Oxidation level

A

the degree of oxidation (loss of electrons) of an atom in a chemical compound

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48
Q

Define

Ozonolysis

A

an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone

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49
Q

Define

Pericyclic chemistry

A

a type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap in a continuous cycle at the transition state

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50
Q

Define

Polarisation

A

The partial or complete polar separation of the positive and negative electric charges in a nuclear, atomic, molecular, or chemical system

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51
Q

Define

Reduction

A

a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen

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52
Q

Define

Regioselectivity

A

the preference of one direction of chemical bond making or breaking over all other possible directions

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53
Q

Define

Resonance

A

a way of describing bonding in certain molecules or ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory

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54
Q

Define

Sigmatropic reactions

A

a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecular process

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55
Q

Define

Stereoselectivity

A

preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant

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56
Q

Define

Swern oxidation

A

a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine.

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57
Q

Define

Tautomers

A

constitutional isomers of chemical compounds that readily interconvert

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58
Q

Definition

electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond

A

Electron delocalisation

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59
Q

Definition

an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile

A

Electrophilic aromatic substitution

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60
Q

Definition

The property of being electrophilic

A

Electrophilicity

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61
Q

Definition

an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine

A

Enamines

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62
Q

Definition

an organic compound that contains a hydroxyl group bonded to a carbon atom having a double bond and that is usually characterized by the grouping C=C(OH)

A

Enol

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63
Q

Definition

Salts of enols (or of the tautomeric aldehydes or ketones), in which the anionic charge is delocalized over oxygen and carbon, or similar covalent metal derivatives in which the metal is bound to oxygen

A

Enolate

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64
Q
A
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65
Q

Definition

the esterification of a Carboxylic acid by heating it with an alcohol in the presence of a strong acid as the catalyst

A

Fischer esterification

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66
Q

Definition

an organometallic chemical reaction in which alkyl, vinyl, or aryl-magnesium halides (Grignard reagent) add to a carbonyl group in an aldehyde or ketone

A

Grignard reaction

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67
Q

Definition

any atom that is not carbon or hydrogen

A

Heteroatom

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68
Q

Definition

a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element

A

Hydrate

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69
Q

Definition

a carbocation rearrangement in which a hydrogen atom in a carbocation migrates to the carbon atom bearing the formal charge of +1 (carbon 2) from an adjacent carbon (carbon 1)

A

Hydride shift

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70
Q

Definition

a functional group or chemical compound containing a carbon–nitrogen double bond

A

Imine

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71
Q

Definition

a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol (an alcohol). The keto and enol forms are said to be tautomers of each other.

A

Keto-enol tautomerisation

72
Q

Definition

a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.

A

Leaving group

73
Q

Definition

  • a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
A

Nucleophile

74
Q

Definition

a class of substitution reactions involving nucleophiles andacyl compounds. In this type of reaction, a nucleophile – such as an alcohol, amine, or enolate – displaces the leaving group of an acyl derivative – such as an acid halide, anhydride, or ester

A

Nucleophilic acyl addition

75
Q

Definition

a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen

A

Oxidation

76
Q

Definition

the degree of oxidation (loss of electrons) of an atom in a chemical compound

A

Oxidation level

77
Q

Definition

an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone

A

Ozonolysis

78
Q

Definition

a type of organic reaction wherein the transition state of the molecule has a cyclic geometry, the reaction progresses in a concerted fashion, and the bond orbitals involved in the reaction overlap in a continuous cycle at the transition state

A

Pericyclic chemistry

79
Q

Definition

The partial or complete polar separation of the positive and negative electric charges in a nuclear, atomic, molecular, or chemical system

A

Polarisation

80
Q

Definition

a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen

A

Reduction

81
Q

Definition

the preference of one direction of chemical bond making or breaking over all other possible directions

A

Regioselectivity

82
Q

Definition

a way of describing bonding in certain molecules or ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory

A

Resonance

83
Q

Definition

a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecular process

A

Sigmatropic reactions

84
Q

Definition

preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant

A

Stereoselectivity

85
Q

Definition

a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine.

A

Swern oxidation

86
Q

Definition

constitutional isomers of chemical compounds that readily interconvert

A

Tautomers

87
Q

Molecules containing carbonyl groups show strong IR absorption frequencis in the region ____________

A

Molecules containing carbonyl groups show strong IR absorption frequencis in the region 1850 - 1630 cm-1​​

88
Q

What type of reaction is the conversion of an aldehyde into an alcohol?

A

Reduction

89
Q

How many oxidation levels are there?

A

5

90
Q

What is more oxidised?

Alcohols or esters

A

Esters

91
Q

What is more oxidised?

Carboxylic acid or ketone

A

Carboxylic acid

92
Q

If the number of C-H bonds has increased, or a reduction in the number of bonds to heteroatoms, then a __________ has occurred

A

If the number of C-H bonds has increased, or a reduction in the number of bonds to heteroatoms, then a reduction has occurred

93
Q

If the number of C-H bonds has decreased, or a increase in the number of bonds to heteroatoms, then a __________ has occurred

A

If the number of C-H bonds has decreased, or a increase in the number of bonds to heteroatoms, then a oxidation has occurred

94
Q

The product of the addition of water to an alkene is neither an oxidation or a reduction. Why?

A

The product of the addition of water to an alkene has one more C-O bond (oxidation) and one more C-H bond (reduction); the two cancel each other out and thus, the reaction is neither an oxidation or reduction

95
Q

List in order of increasing reactivity with nucleophiles:

Aldehyde, amide, carboxylate, ester and ketone

A

Aldehyde > ketone > ester > amide > carboxylate

(think about electron delocalisation; resonance = stability)

96
Q

Why are amides and carboxylic acids so unreactive?

A

They are resonance stabilised; electron density is spread out over a number of nuclei which makes it less electrophilic

97
Q

What are the two mechanistic steps of nucleophilic acyl addition?

A
  1. Attack of nucleophile, breakage of π-bond to give charged sp3 intermediate
  2. Protonation of intermediate to give product
98
Q

What is the general formula for the Grignard reagent?

A

R2MgBr

99
Q

In the Grignard reaction:

Additions to formaledehyde (CH2O) give ____________

Additions to aldehydes (RCHO) give ___________

Additions to ketones (R2CO) give ___________

Additions to esters (RCO2R) to give ______________

A

In the Grignard reaction:

Additions to formaledehyde (CH2O) give primary alcohols

Additions to aldehydes (RCHO) give secondary alcohols

Additions to ketones (R2CO) give tertiary alcohols

Additions to esters (RCO2R) to give tertiary alcohols with two equivalent R groups

100
Q

Nucleophilic acyl addition of:

  1. Water gives ____________
  2. Cyanide gives ____________
  3. Grignard reagents gives ___________
A

Nucleophilic acyl addition of:

  1. Water gives 1,1-diols or hydrates
  2. Cyanide gives cyanohydrins
  3. Grignard reagents gives alcohols
101
Q

Aldehydes and ketones react with alcohols to form __________, and react with amines to form ________

A

Aldehydes and ketones react with alcohols to form acetals, and react with amines to form imines

102
Q

Draw the product and the mechanism of this reaction

A
103
Q

Draw the product and the mechanism of this reaction

A
104
Q

Acid catalysts make the electrophile ____________

Base catalysts make the nucleophile ____________

A

Acid catalysts make the electrophile more electrophilic

Base catalysts make the nucleophile more nucleophilic

105
Q

List these in increasing order of leaving group quality:

Acyl chloride, alkyl or aryl, amide, anhydride, ester

A

Acyl chloride > anhydride > ester > amide > alkyl or aryl

106
Q

A carboxylic acid derivative will undergo a nucleophilic acyl substitution when?

A

A carboxylic acid derivative will undergo a nucleophilic acyl substitution provided the incoming nucleophile is a stronger base than the substituent attached to the acyl group

107
Q

How are C=O compounds synthesised?

A
  1. Oxidation of alcohols
  2. Oxidation of alkenes to give two C=O compounds
108
Q

Oxidation of:

Primary alcohols give _________

Secondary alcohols give _________

Tertiarty alcohols give _________

A

Oxidation of:

Primary alcohols give aldehydes (which can be oxidised further to carboxylic acid and CO2)

Secondary alcohols give ketones

Tertiarty alcohols give tertiary alcohols (oxidation not possible)

109
Q

What are primary alcohols oxidised to in the presence of metals in high oxidation states (Cr(VI) and Mn(VII))?

A

Carboxylic acids

110
Q

A primary alcohol, DMSO, base and electrophile are present. What reaction would occur?

A

Swern oxidation

Alcohol to aldehyde

111
Q

A primary and secondary alcohol is oxidised under Jones conditions. What products would form?

A

Carboxylic acid (from 1°)

Ketones (from 2°)

112
Q

A primary and secondary alcohol is oxidised under Swern conditions. What products would form?

A

Aldehyde (from 1°)

Ketone (from 2°)

113
Q

Reductive ozonolysis of alkenes results in what products?

i.e. R1C=CR2 (O3, Me2S)

A

2 corresponding aldehydes

i.e. R1C=O and O=CR2

114
Q

Oxidative ozonolysis of alkenes results in what products?

i.e. R1C=CR2 (O3, H2O2)

A

2 corresponding carboxylic acids

i.e. R1COOH and R2COOH

115
Q

Ozonolysis of RC=CH2 (i.e. terminal alkene) in the presence of Me2S would give which products?

A

RC=O and H2C=O (formaldehyde)

116
Q
A
117
Q

Oxidative cleavage of terminal alkynes give what?

A

C=O compound and CO2

118
Q

List these groups in order of increasing ease in reduction:

Aldehyde, amide, carboxylate, ester, ketone

A

Aldehyde > ketone > ester > amide > carboxylate

119
Q

Reduction of which compounds give 1° alcohols?

A

Aldehydes

Esters

Carboxylic acids

120
Q

How are carbonyl groups selectively reduced?

A

Using a hydride transfer reagent (i.e. NaBH4, LiBH4)

121
Q

Sodium borohydride, NaBH4, reduces which carbonyl compounds? Which does it not reduce?

A

Reduces aldehydes and ketones to alcohols

Will not reduce esters, carboxylic acids and amides

122
Q

Lithium borohydride, LiBH4, reduces which carbonyl compounds? Which does it not reduce?

A

Reduces aldehydes, ketones and esters to alcohols

Won’t reduce amides or carboxylic acids

123
Q

What is a protective group?

A

A protective group is a functional group that makes another group incapable of taking part in a reaction, which can be installed and removed easily in high yields

124
Q

Acid catalysed enolisation gives an _______

Base catalysed enolisation gives an _______

A

Acid catalysed enolisation gives an enol

Base catalysed enolisation gives an enolate

125
Q

What does the strength of the base used during enolisation do to the reaction?

A

Strong base = drive equilibrium to the formation of the enolate

Weak base = enolate is in equilibrium with keto form

126
Q

Thermodynamic enolates are favoured by what?

A
  • Unhindered bases
  • Adding base to ketone
  • High temeprature and longer reaction time
127
Q

Kinetic enolates are favoured by what?

A
  • Hindered bulky bases
  • Adding ketone to the base
  • Lower temperature and short reaction times
128
Q

What is the kinetic and thermodynamic enolates?

A

Kinetic enolate = less substrituted, less stable enolate

Thermodynamic enolate = more substituted, more stable

129
Q

Draw a mechanism for CH3CH=O undergoing an aldol reaction

A
130
Q

For crossed aldol reactions to work, what conditions must be met?

A
  • Only one partnes must be capable of enolisation
  • The other partnes must be incapable of enolisation and be more electrophilic than the other
131
Q

How is tautomerisation different to resonance?

A

Tautomerisation involves breaking and making bonds. Resonance does not

132
Q

Electron donating groups (O, N and alkyl) _______ benzene rings

Electron withdrawing groups (NO2, CF3, CN and acyl) _______ benzene rings

A

Electron donating groups (O, N and alkyl) activate benzene rings

Electron withdrawing groups (NO2, CF3, CN and acyl) deactivate benzene rings

133
Q

What is true for all pericyclic reactions?

A
  1. Concerted: single step, one transition state, no intermediates, cyclic re-distribution of bonding electrons
  2. Highly stereospecific: depends on stereochemistry of reactants, number of bonds in reactants, conditions
134
Q

For a Diels-Alder reaction to occur, the diene must be in which conformation?

A

s-cis conformation

135
Q

How do you recognise a Diels-Alder product?

A

It is a six-membered ring

There is a double bond in the ring

There is a conjugating group outisde the ring opposite to the double bond

136
Q

What are the three classes of pericyclic reactions?

A

Cycloadditions

Sigmatropic rearrangments

Electrocyclic reactions

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CHM2911 (4 decks)

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