Organic Chemistry II Flashcards
Define
Acetal
an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule
Define
Acyl
denoting a radical of general formula —C(O)R, where R is an alkyl group, derived from a carboxylic acid
Define
Aldol condensation
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
Define
Aldol reaction
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
Define
Bond hybridisation
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
Define
Carbonyl
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
Define
Chemoselectivity
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
Define
Claisen ester condensation
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
Define
Claisen rearrangement
a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen
Define
Conjugation
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
Define
Cope rearrangement
the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene
Define
Cycloaddition reactions
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.”
Define
De-shielded
A nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects
Define
Diels-Alder reaction
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
Definition
an organic compound formed by the condensation of two alcohol molecules with an aldehyde molecule
Acetal
Definition
denoting a radical of general formula —C(O)R, where R is an alkyl group, derived from a carboxylic acid
Acyl
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
Aldol condensation
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
Aldol reaction
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
Bond hybridisation
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
Carbonyl
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
Chemoselectivity
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
Claisen ester condensation
Definition
a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen
Claisen rearrangement
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
Conjugation
Definition
the thermal isomerization of a 1,5-diene leading to a regioisomeric 1,5-diene
Cope rearrangement
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
Definition
A nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects
De-shielded
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
Define
Electron delocalisation
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond
Define
Electrophilic aromatic substitution
an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile
Define
Electrophilicity
The property of being electrophilic
Define
Enamines
an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine
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)
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
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
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
Define
Heteroatom
any atom that is not carbon or hydrogen
Define
Hydrate
a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element
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)
Define
Imine
a functional group or chemical compound containing a carbon–nitrogen double bond
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.
Define
Leaving group
a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.
Define
Nucleophile
- a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
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
Define
Oxidation
a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen
Define
Oxidation level
the degree of oxidation (loss of electrons) of an atom in a chemical compound
Define
Ozonolysis
an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone
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
Define
Polarisation
The partial or complete polar separation of the positive and negative electric charges in a nuclear, atomic, molecular, or chemical system
Define
Reduction
a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen
Define
Regioselectivity
the preference of one direction of chemical bond making or breaking over all other possible directions
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
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
Define
Stereoselectivity
preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant
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.
Define
Tautomers
constitutional isomers of chemical compounds that readily interconvert
Definition
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond
Electron delocalisation
Definition
an organic reaction in which an atom that is attached to anaromatic system (usually hydrogen) is replaced by an electrophile
Electrophilic aromatic substitution
Definition
The property of being electrophilic
Electrophilicity
Definition
an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine
Enamines
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
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
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
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
Definition
any atom that is not carbon or hydrogen
Heteroatom
Definition
a compound, typically a crystalline one, in which water molecules are chemically bound to another compound or an element
Hydrate
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
Definition
a functional group or chemical compound containing a carbon–nitrogen double bond
Imine
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
Definition
a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage.
Leaving group
Definition
- a molecule or substance that has a tendency to donate electrons or react at electron-poor sites such as protons
Nucleophile
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
Definition
a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen
Oxidation
Definition
the degree of oxidation (loss of electrons) of an atom in a chemical compound
Oxidation level
Definition
an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone
Ozonolysis
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
Definition
The partial or complete polar separation of the positive and negative electric charges in a nuclear, atomic, molecular, or chemical system
Polarisation
Definition
a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen
Reduction
Definition
the preference of one direction of chemical bond making or breaking over all other possible directions
Regioselectivity
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
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
Definition
preferentially producing a particular stereoisomeric form of the product, irrespective of the configuration of the reactant
Stereoselectivity
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
Definition
constitutional isomers of chemical compounds that readily interconvert
Tautomers
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
What type of reaction is the conversion of an aldehyde into an alcohol?
Reduction
How many oxidation levels are there?
5
What is more oxidised?
Alcohols or esters
Esters
What is more oxidised?
Carboxylic acid or ketone
Carboxylic acid
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
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
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
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)
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
What are the two mechanistic steps of nucleophilic acyl addition?
- Attack of nucleophile, breakage of π-bond to give charged sp3 intermediate
- Protonation of intermediate to give product
What is the general formula for the Grignard reagent?
R2MgBr
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
Nucleophilic acyl addition of:
- Water gives ____________
- Cyanide gives ____________
- Grignard reagents gives ___________
Nucleophilic acyl addition of:
- Water gives 1,1-diols or hydrates
- Cyanide gives cyanohydrins
- Grignard reagents gives alcohols
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
Draw the product and the mechanism of this reaction
Draw the product and the mechanism of this reaction
Acid catalysts make the electrophile ____________
Base catalysts make the nucleophile ____________
Acid catalysts make the electrophile more electrophilic
Base catalysts make the nucleophile more nucleophilic
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
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
How are C=O compounds synthesised?
- Oxidation of alcohols
- Oxidation of alkenes to give two C=O compounds
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)
What are primary alcohols oxidised to in the presence of metals in high oxidation states (Cr(VI) and Mn(VII))?
Carboxylic acids
A primary alcohol, DMSO, base and electrophile are present. What reaction would occur?
Swern oxidation
Alcohol to aldehyde
A primary and secondary alcohol is oxidised under Jones conditions. What products would form?
Carboxylic acid (from 1°)
Ketones (from 2°)
A primary and secondary alcohol is oxidised under Swern conditions. What products would form?
Aldehyde (from 1°)
Ketone (from 2°)
Reductive ozonolysis of alkenes results in what products?
i.e. R1C=CR2 (O3, Me2S)
2 corresponding aldehydes
i.e. R1C=O and O=CR2
Oxidative ozonolysis of alkenes results in what products?
i.e. R1C=CR2 (O3, H2O2)
2 corresponding carboxylic acids
i.e. R1COOH and R2COOH
Ozonolysis of RC=CH2 (i.e. terminal alkene) in the presence of Me2S would give which products?
RC=O and H2C=O (formaldehyde)
Oxidative cleavage of terminal alkynes give what?
C=O compound and CO2
List these groups in order of increasing ease in reduction:
Aldehyde, amide, carboxylate, ester, ketone
Aldehyde > ketone > ester > amide > carboxylate
Reduction of which compounds give 1° alcohols?
Aldehydes
Esters
Carboxylic acids
How are carbonyl groups selectively reduced?
Using a hydride transfer reagent (i.e. NaBH4, LiBH4)
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
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
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
Acid catalysed enolisation gives an _______
Base catalysed enolisation gives an _______
Acid catalysed enolisation gives an enol
Base catalysed enolisation gives an enolate
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
Thermodynamic enolates are favoured by what?
- Unhindered bases
- Adding base to ketone
- High temeprature and longer reaction time
Kinetic enolates are favoured by what?
- Hindered bulky bases
- Adding ketone to the base
- Lower temperature and short reaction times
What is the kinetic and thermodynamic enolates?
Kinetic enolate = less substrituted, less stable enolate
Thermodynamic enolate = more substituted, more stable
Draw a mechanism for CH3CH=O undergoing an aldol reaction
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
How is tautomerisation different to resonance?
Tautomerisation involves breaking and making bonds. Resonance does not
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
What is true for all pericyclic reactions?
- Concerted: single step, one transition state, no intermediates, cyclic re-distribution of bonding electrons
- Highly stereospecific: depends on stereochemistry of reactants, number of bonds in reactants, conditions
For a Diels-Alder reaction to occur, the diene must be in which conformation?
s-cis conformation
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
What are the three classes of pericyclic reactions?
Cycloadditions
Sigmatropic rearrangments
Electrocyclic reactions
