Organic Chemistry II Flashcards
(177 cards)
1
Q
Define
Acetal
A
an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule
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
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
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
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
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
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
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
9
Q
Define
Claisen rearrangement
A
a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen
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
11
Q
Define
Cope rearrangement
A
the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene
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.”
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
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
15
Q
Definition
an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule
A
Acetal
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
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
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
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
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
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
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
23
Q
Definition
a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen
A
Claisen rearrangement
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
25
# Definition
the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene
Cope rearrangement
26
# 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."
Cycloaddition reactions
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# Definition
A nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects
De-shielded
28
# 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
Diels-Alder reaction
29
# Define
Electron delocalisation
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond
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# Define
Electrophilic aromatic substitution
an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile
31
# Define
Electrophilicity
The property of being electrophilic
32
# Define
Enamines
an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine
33
# Define
Enol
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)
34
# Define
Enolate
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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# Define
Fischer esterification
the esterification of a Carboxylic acid by heating it with an alcohol in the presence of a strong acid as the catalyst
37
# Define
Grignard reaction
an organometallic chemical reaction in which alkyl, vinyl, or aryl-magnesium halides (Grignard reagent) add to a carbonyl group in an aldehyde or ketone
38
# Define
Heteroatom
any atom that is not carbon or hydrogen
39
# Define
Hydrate
a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element
40
# Define
Hydride shift
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)
41
# Define
Imine
a functional group or chemical compound containing a carbon–nitrogen double bond
42
# Define
Keto-enol tautomerisation
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.
43
# Define
Leaving group
a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.
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# Define
Nucleophile
- a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
45
# Define
Nucleophilic acyl addition
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
46
# Define
Oxidation
a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen
47
# Define
Oxidation level
the degree of oxidation (loss of electrons) of an atom in a chemical compound
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# Define
Ozonolysis
an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone
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# Define
Pericyclic chemistry
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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# Define
Polarisation
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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# Define
Reduction
a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen
52
# Define
Regioselectivity
the preference of one direction of chemical bond making or breaking over all other possible directions
53
# Define
Resonance
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
54
# Define
Sigmatropic reactions
a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecular process
55
# Define
Stereoselectivity
preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant
56
# Define
Swern oxidation
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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# Define
Tautomers
constitutional isomers of chemical compounds that readily interconvert
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# Definition
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond
Electron delocalisation
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# Definition
an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile
Electrophilic aromatic substitution
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# Definition
The property of being electrophilic
Electrophilicity
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# Definition
an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine
Enamines
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# 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)
Enol
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# 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
Enolate
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# Definition
the esterification of a Carboxylic acid by heating it with an alcohol in the presence of a strong acid as the catalyst
Fischer esterification
66
# 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
Grignard reaction
67
# Definition
any atom that is not carbon or hydrogen
Heteroatom
68
# Definition
a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element
Hydrate
69
# 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)
Hydride shift
70
# Definition
a functional group or chemical compound containing a carbon–nitrogen double bond
Imine
71
# 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.
Keto-enol tautomerisation
72
# Definition
a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.
Leaving group
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# Definition
- a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
Nucleophile
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# 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
Nucleophilic acyl addition
75
# Definition
a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen
Oxidation
76
# Definition
the degree of oxidation (loss of electrons) of an atom in a chemical compound
Oxidation level
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# Definition
an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone
Ozonolysis
78
# 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
Pericyclic chemistry
79
# Definition
The partial or complete polar separation of the positive and negative electric charges in a nuclear, atomic, molecular, or chemical system
Polarisation
80
# Definition
a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen
Reduction
81
# Definition
the preference of one direction of chemical bond making or breaking over all other possible directions
Regioselectivity
82
# 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
Resonance
83
# Definition
a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecular process
Sigmatropic reactions
84
# Definition
preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant
Stereoselectivity
85
# 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.
Swern oxidation
86
# Definition
constitutional isomers of chemical compounds that readily interconvert
Tautomers
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Molecules containing carbonyl groups show strong IR absorption frequencis in the region \_\_\_\_\_\_\_\_\_\_\_\_
Molecules containing carbonyl groups show strong IR absorption frequencis in the region **1850 - 1630 cm-1**
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What type of reaction is the conversion of an aldehyde into an alcohol?
Reduction
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How many oxidation levels are there?
5
90
What is more oxidised?
Alcohols or esters
Esters
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What is more oxidised?
Carboxylic acid or ketone
Carboxylic acid
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If the number of C-H bonds has increased, or a reduction in the number of bonds to heteroatoms, then a __________ has occurred
If the number of C-H bonds has increased, or a reduction in the number of bonds to heteroatoms, then a **reduction** has occurred
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If the number of C-H bonds has decreased, or a increase in the number of bonds to heteroatoms, then a __________ has occurred
If the number of C-H bonds has decreased, or a increase in the number of bonds to heteroatoms, then a **oxidation** has occurred
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The product of the addition of water to an alkene is neither an oxidation or a reduction. Why?
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
List in order of increasing reactivity with nucleophiles:
Aldehyde, amide, carboxylate, ester and ketone
Aldehyde \> ketone \> ester \> amide \> carboxylate
(think about electron delocalisation; resonance = stability)
96
Why are amides and carboxylic acids so unreactive?
They are resonance stabilised; electron density is spread out over a number of nuclei which makes it less electrophilic
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What are the two mechanistic steps of nucleophilic acyl addition?
1. Attack of nucleophile, breakage of π-bond to give charged sp3 intermediate
2. Protonation of intermediate to give product
98
What is the general formula for the Grignard reagent?
R2MgBr
99
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 \_\_\_\_\_\_\_\_\_\_\_\_\_\_
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
Nucleophilic acyl addition of:
1. Water gives \_\_\_\_\_\_\_\_\_\_\_\_
2. Cyanide gives \_\_\_\_\_\_\_\_\_\_\_\_
3. Grignard reagents gives \_\_\_\_\_\_\_\_\_\_\_
Nucleophilic acyl addition of:
1. Water gives **1,1-diols or** **hydrates**
2. Cyanide gives **cyanohydrins**
3. Grignard reagents gives **alcohols**
101
Aldehydes and ketones react with alcohols to form \_\_\_\_\_\_\_\_\_\_, and react with amines to form \_\_\_\_\_\_\_\_
Aldehydes and ketones react with alcohols to form **acetals**, and react with amines to form **imines**
102
Draw the product and the mechanism of this reaction
103
Draw the product and the mechanism of this reaction
104
Acid catalysts make the electrophile \_\_\_\_\_\_\_\_\_\_\_\_
Base catalysts make the nucleophile \_\_\_\_\_\_\_\_\_\_\_\_
Acid catalysts make the electrophile **more electrophilic**
Base catalysts make the nucleophile **more nucleophilic**
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List these in increasing order of leaving group quality:
Acyl chloride, alkyl or aryl, amide, anhydride, ester
Acyl chloride \> anhydride \> ester \> amide \> alkyl or aryl
106
A carboxylic acid derivative will undergo a nucleophilic acyl substitution when?
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
How are C=O compounds synthesised?
1. Oxidation of alcohols
2. Oxidation of alkenes to give two C=O compounds
108
Oxidation of:
Primary alcohols give \_\_\_\_\_\_\_\_\_
Secondary alcohols give \_\_\_\_\_\_\_\_\_
Tertiarty alcohols give \_\_\_\_\_\_\_\_\_
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
What are primary alcohols oxidised to in the presence of metals in high oxidation states (Cr(VI) and Mn(VII))?
Carboxylic acids
110
A primary alcohol, DMSO, base and electrophile are present. What reaction would occur?
Swern oxidation
Alcohol to aldehyde
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A primary and secondary alcohol is oxidised under Jones conditions. What products would form?
Carboxylic acid (from 1°)
Ketones (from 2°)
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A primary and secondary alcohol is oxidised under Swern conditions. What products would form?
Aldehyde (from 1°)
Ketone (from 2°)
113
Reductive ozonolysis of alkenes results in what products?
i.e. R1C=CR2 (O3, Me2S)
2 corresponding aldehydes
i.e. R1C=O and O=CR2
114
Oxidative ozonolysis of alkenes results in what products?
i.e. R1C=CR2 (O3, H2O2)
2 corresponding carboxylic acids
i.e. R1COOH and R2COOH
115
Ozonolysis of RC=CH2 (i.e. terminal alkene) in the presence of Me2S would give which products?
RC=O and H2C=O (formaldehyde)
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Oxidative cleavage of terminal alkynes give what?
C=O compound and CO2
118
List these groups in order of increasing ease in reduction:
Aldehyde, amide, carboxylate, ester, ketone
Aldehyde \> ketone \> ester \> amide \> carboxylate
119
Reduction of which compounds give 1° alcohols?
Aldehydes
Esters
Carboxylic acids
120
How are carbonyl groups selectively reduced?
Using a hydride transfer reagent (i.e. NaBH4, LiBH4)
121
Sodium borohydride, NaBH4, reduces which carbonyl compounds? Which does it not reduce?
Reduces _aldehydes_ and _ketones_ to alcohols
Will not reduce esters, carboxylic acids and amides
122
Lithium borohydride, LiBH4, reduces which carbonyl compounds? Which does it not reduce?
Reduces _aldehydes, ketones_ and _esters_ to alcohols
Won't reduce amides or carboxylic acids
123
What is a protective group?
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
Acid catalysed enolisation gives an \_\_\_\_\_\_\_
Base catalysed enolisation gives an \_\_\_\_\_\_\_
Acid catalysed enolisation gives an **enol**
Base catalysed enolisation gives an **enolate**
125
What does the strength of the base used during enolisation do to the reaction?
Strong base = drive equilibrium to the formation of the enolate
Weak base = enolate is in equilibrium with keto form
126
Thermodynamic enolates are favoured by what?
* Unhindered bases
* Adding base to ketone
* High temeprature and longer reaction time
127
Kinetic enolates are favoured by what?
* Hindered bulky bases
* Adding ketone to the base
* Lower temperature and short reaction times
128
What is the kinetic and thermodynamic enolates?
Kinetic enolate = less substrituted, less stable enolate
Thermodynamic enolate = more substituted, more stable
129
Draw a mechanism for CH3CH=O undergoing an aldol reaction
130
For crossed aldol reactions to work, what conditions must be met?
* Only one partnes must be capable of enolisation
* The other partnes must be incapable of enolisation and be more electrophilic than the other
131
How is tautomerisation different to resonance?
Tautomerisation involves breaking and making bonds. Resonance does not
132
Electron donating groups (O, N and alkyl) _______ benzene rings
Electron withdrawing groups (NO2, CF3, CN and acyl) _______ benzene rings
Electron donating groups (O, N and alkyl) **activate** benzene rings
Electron withdrawing groups (NO2, CF3, CN and acyl) **deactivate** benzene rings
133
What is true for all pericyclic reactions?
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
For a Diels-Alder reaction to occur, the diene must be in which conformation?
s-*cis* conformation
135
How do you recognise a Diels-Alder product?
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
What are the three classes of pericyclic reactions?
Cycloadditions
Sigmatropic rearrangments
Electrocyclic reactions
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