Organic Chemistry I Flashcards
Define
Anti-periplanar
describes two bonds that are antiparallel in the plane they define (i.e. C-H and C-LG bonds)
Define
Backside attack
The SN2 mechanism in which the nucleophile attacks the α-carbon from a direction directly opposite to the C-LG bond. Results in inversion of stereochemical configuration
Define
Bromination
Any reaction or process in which bromine (and no other elements) are introduced into a molecule
Define
Carboanion
an organic anion in which the negative charge is located on a carbon atom
Define
Carbocation
A carbon that carries a positive charge. They are highly unstable and are prone to rearrangement. SN1 and E1 reactions proceed through this common intermediate
Define
Chirality
The geometric property of a rigid object (or spatial arrangement of points or atoms) of being non-superposable on its mirror image
Define
Concerted
A single step mechanism. Describes SN2 and E2 mechanisms
Define
E1 reaction
A reaction where a β-hydrogen is Eliminated to form a double bond. They go through a carbocation intermediate. Somewhat similar to the E2 reaction
Define
E2 reaction
reaction in which a β-hydrogen and a leaving group are removed to form a double bond. The reaction is so named because it is bimolecular (2 molecules) and because it involves the Elimination of a β-hydrogen
Define
Electron delocalisation
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond
Define
Electrophile
an electron pair acceptor. They are positively charged or neutral species having vacant orbitals that are attracted to an electron rich centre. It participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile
Define
Electrophilic addition
a reaction between an electrophile and nucleophile, adding to double or triple bonds
Define
Elimination reaction
a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism
Define
Finkelstein reaction
an SN2reaction (Substitution Nucleophilic Bimolecular reaction) that involves the exchange of one halogen atom for another
Define
First-order reaction
a chemical reaction in which the rate of reaction is directly proportional to the concentration of the reacting substance
Define
Frontside attack
A disproved SN2 mechanism in which the nucleophile attacks the α-carbon from the same side as the C-LG bond. If this mechanism was valid, it would result in retention of stereochemical configuration
Define
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
Hydroboration
the addition of a hydrogen-boron bond to C-C, C-N, and C-O double bonds, as well as C-C triple bonds
Define
Hyperconjugation
the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system
Define
Lewis structure
a diagram that shows the covalent bonds and lone electron pairs in a molecule
Define
Markivnikov’s rule
In an addition reaction of a protic acid HX (hydrogen chloride, hydrogen bromide, or hydrogen iodide) to an alkene or alkyne, the hydrogen atom of HX becomes bonded to the carbon atom that had the greatest number of hydrogen atoms in the starting alkene or alkyne
Define
Mecuriation
Any reaction that introduces a covalent mercury bond into a compound
Define
Nucleophile
a chemical species that donates an electron pair to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as one. Because they donate electrons, they are by definition Lewis bases
Define
Nucleophilic substitution reactions
a fundamental class of reactions in which an electron rich nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms to replace a leaving group
Define
Oxymecuration
an electrophilic addition organic reaction that transforms an alkene into a neutral alcohol
Define
Radical
an atom, molecule, or ion that has an unpaired valence electron
Define
Reactive intermediates
a molecular entity that is formed from the reactants (or preceding intermediates) and reacts further to give the directly observed products of a chemical reaction
Define
Rearrangment reactions
a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule
Define
Regioselectivity
the preference of one direction of chemical bond making or breaking over all other possible directions
Define
Second-order reaction
a type of chemical reaction that depends on the concentrations of one-second order reactant or two first-order reactants. This reaction proceeds at a rate proportional to the square of the concentration of one reactant or the product of the concentrations of two reactants
Define
SN1 reaction
A reaction in which a Nucleophile Substitutes for a leaving group. It goes through a carbocation intermediate
Define
SN2 reaction
reaction is a bimolecular (2 molecules) reaction involving the Substitution of a Nucleophile for a leaving group
Define
Sp hybridisation
a type of hybridization where the s orbital overlaps with only one p orbital
Define
Sp2 hybridisation
The process of intermixing of one S and two P orbitals to give three identical hybrid orbitals
Define
Sp3 hybridisation
refers to the mixing of one s and three p orbitals to form four sp3 hybridized orbitals
Define
Stereogenic centre
any location in a molecule where the interchange of any two groups gives a new stereoisomer
Define
Stereoselectivity
the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non-stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one
Define
Steric effects
an influence on a reaction’s course or rate determined by the fact that all of the atoms within a molecule occupy space, thus certain collision paths are either disfavored or favored
Define
Zaitsev rule
an empirical rule for predicting the favored alkene product(s) in elimination reactions
Definition
describes two bonds that are antiparallel in the plane they define (i.e. C-H and C-LG bonds)
Anti-periplanar
Definition
The SN2 mechanism in which the nucleophile attacks the α-carbon from a direction directly opposite to the C-LG bond. Results in inversion of stereochemical configuration
Backside attack
Definition
Any reaction or process in which bromine (and no other elements) are introduced into a molecule
Bromination
Definition
an organic anion in which the negative charge is located on a carbon atom
Carboanion
Definition
A carbon that carries a positive charge. They are highly unstable and are prone to rearrangement. SN1 and E1 reactions proceed through this common intermediate
Carbocation
Definition
The geometric property of a rigid object (or spatial arrangement of points or atoms) of being non-superposable on its mirror image
Chirality
Definition
A single step mechanism. Describes SN2 and E2 mechanisms
Concerted
Definition
A reaction where a β-hydrogen is Eliminated to form a double bond. They go through a carbocation intermediate. Somewhat similar to the E2 reaction
E1 reaction
Definition
reaction in which a β-hydrogen and a leaving group are removed to form a double bond. The reaction is so named because it is bimolecular (2 molecules) and because it involves the Elimination of a β-hydrogen
E2 reaction
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 electron pair acceptor. They are positively charged or neutral species having vacant orbitals that are attracted to an electron rich centre. It participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile
Electrophile
Definition
a reaction between an electrophile and nucleophile, adding to double or triple bonds
Electrophilic addition
Definition
a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism
Elimination reaction
Definition
an SN2reaction (Substitution Nucleophilic Bimolecular reaction) that involves the exchange of one halogen atom for another
Finkelstein reaction
Definition
a chemical reaction in which the rate of reaction is directly proportional to the concentration of the reacting substance
First-order reaction
Definition
A disproved SN2 mechanism in which the nucleophile attacks the α-carbon from the same side as the C-LG bond. If this mechanism was valid, it would result in retention of stereochemical configuration
Frontside attack
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
Hybridisation
Definition
the addition of a hydrogen-boron bond to C-C, C-N, and C-O double bonds, as well as C-C triple bonds
Hydroboration
Definition
the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π-orbital to give an extended molecular orbital that increases the stability of the system
Hyperconjugation
Definition
a diagram that shows the covalent bonds and lone electron pairs in a molecule
Lewis structure
Definition
In an addition reaction of a protic acid HX (hydrogen chloride, hydrogen bromide, or hydrogen iodide) to an alkene or alkyne, the hydrogen atom of HX becomes bonded to the carbon atom that had the greatest number of hydrogen atoms in the starting alkene or alkyne
Markivnikov’s rule
Definition
Any reaction that introduces a covalent mercury bond into a compound
Mecuriation
Definition
a chemical species that donates an electron pair to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as one. Because they donate electrons, they are by definition Lewis bases
Nucleophile
Definition
a fundamental class of reactions in which an electron rich nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms to replace a leaving group
Nucleophilic substitution reactions
Definition
an electrophilic addition organic reaction that transforms an alkene into a neutral alcohol
Oxymecuration
Definition
an atom, molecule, or ion that has an unpaired valence electron
Radical
Definition
a molecular entity that is formed from the reactants (or preceding intermediates) and reacts further to give the directly observed products of a chemical reaction
Reactive intermediates
Definition
a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule
Rearrangment reactions
Definition
the preference of one direction of chemical bond making or breaking over all other possible directions
Regioselectivity
Definition
a type of chemical reaction that depends on the concentrations of one-second order reactant or two first-order reactants. This reaction proceeds at a rate proportional to the square of the concentration of one reactant or the product of the concentrations of two reactants
Second-order reaction
Definition
A reaction in which a Nucleophile Substitutes for a leaving group. It goes through a carbocation intermediate
SN1 reaction
Definition
reaction is a bimolecular (2 molecules) reaction involving the Substitution of a Nucleophile for a leaving group
SN2 reaction
Definition
a type of hybridization where the s orbital overlaps with only one p orbital
Sp hybridisation
Definition
The process of intermixing of one S and two P orbitals to give three identical hybrid orbitals
Sp2 hybridisation
Definition
refers to the mixing of one s and three p orbitals to form four sp3 hybridized orbitals
Sp3 hybridisation
Definition
any location in a molecule where the interchange of any two groups gives a new stereoisomer
Stereogenic centre
Definition
the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non-stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one
Stereoselectivity
Definition
an influence on a reaction’s course or rate determined by the fact that all of the atoms within a molecule occupy space, thus certain collision paths are either disfavored or favored
Steric effects
Definition
an empirical rule for predicting the favored alkene product(s) in elimination reactions
Zaitsev rule
What are the three different types of hybridisation that can occur?
How many σ-bonds does sp3 hydridisation have?
4 σ-bonds
s1p3: 1+3=4
What is the bond angle of an sp2 carbon?
120 degrees
In ethene, each C atom has __ sp2 orbital(s) and __ p orbital(s)
In ethene, each C atom has 3 sp2 orbitals and 1 p orbital
What is the bond angle of a sp carbon?
180 degrees
What are the two electron deficient states that a carbon molecule can exist in?
Radical and carbocation
True or False:
Carbocations are electrophilic
True
They are electron deficient and therefore seek out more electrons
True or False:
Carboanions are electrophilic
False
They are nucleophilic since they are electron rich
Carbocations have __ s and __ p orbitals
Carbocations have 1 s and 2 p orbitals
What hybridisation state are carbocations in?
sp2
What hybridisation state are carbon centered radicals in?
sp2
What hybridisation state are carboanions in?
sp3
When drawing resonance contributors, how can electrons be moved?
- Move π electrons toward a positive charge or toward a π bond
- Move lone-pair electrons toward π bond
- Move a single non-bonding electron (or charge) toward a π bond
List the carbocations in order of increasing stability
Why is this the case?
3° > 2° > 1° > methyl
This is because the charge can be delocalised over a greater number of nuclei
____________ donate high-energy electrons to electrophiles
__________ have a low-energy vacant orbital
Nucleophiles donate high-energy electrons to electrophiles
Electrophiles have a low-energy vacant orbital
__________are negatively charged or neutral species with a pair of electrons
____________are neutral or positively charged species with an empty atomic orbital
Nucleophiles are negatively charged or neutral species with a pair of electrons
Electrophiles are neutral or positively charged species with an empty atomic orbital
What happens in a general nucleophilic substitution reaction?
A nucleophile attacks a sp3 hybridised carbon and the leaving group leaves
If a stable carbocation can’t form then a SN1/SN2 (choose one) reaction mechanism is not possible
If a stable carbocation can’t form then a SN1 reaction mechanism is not possible
What reaction mechanism is this?
SN1 mechanism
What reaction mechanism is this?
SN2 mechanism
An SN2 reaction is concerted and hence any 3D stereochemical information is _________ and the stereochemistry of the stereogenic centre that is attacked by the nucleophile is ________
An SN2 reaction is concerted and hence any 3D stereochemical information is maintained and the stereochemistry of the stereogenic centre that is attacked by the nucleophile is inverted
What determines the rate of an SN1 reaction?
The concentration of the alkyl halide
(if the concentration of the alkyl halide doubles, the rate doubles)
What determines the rate of an SN2 reaction?
The rate depends on the concentration of both reagents
(if the concentration of the alkyl halide or the nucleophile doubles, the rate doubles)
What type of solvent favours an SN2 reaction?
A polar, aprotic solvent like DMF or DMSO
What type of solvent favours an SN1 reaction?
A polar, protic solvent like H2O, R-OH, R-COOH
True or False:
During elimination reactions, the nucleophile acts as a base
True
What is the rate of an E1 reaction determined by?
Concentration of alkyl halide only
What is the rate of an E2 reaction determined by?
Concentration of the base and the alkyl halide
Zaitsev rule states that the more substituted alkene product is obtained when?
When a proton is removed from the β-carbon that is bonded to the fewest hydrogens
Why are E-alkenes usually lower in energy?
Due to steric reasons
Why can multiple products be produced in E2 reactions?
Often there are 2 β-carbons with hydrogens that could be targeted by the base
True or False:
E2 eliminations have anti-periplanr transition states
True
True or False:
Both E1 and E2 always favour the formation of the more substituted alkene
False;
E1 reactions give the more substitutened alkene
E2 reactions give the more substituted alkene, but are regioselective for the less substituted alkene if a hindered base is used
Is ΔS higher for elimination or substitution reactions?
Elimination (2 become 3; whereas in substitution 2 become 2)
Markovnikov’s rule states that the hydrogen ends up attached to the carbn of the double bond that has what?
Had more hydrogens to start with
