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Chapter 7
Further Reactions of Haloalkanes
51
Organic Chemistry
Undergraduate 2
10/19/2014

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Term
The fact that the rate of the SN2 reaction diminishes drastically when the reacting center changes from primary to secondary to tertiary pertains only to _____ substitution
Definition
bimolecular
Term
Solvolysis is a transformation in which a substrate undergoes substitution by _____ molecules
Definition
solvent
Term
hydrolysis
Definition
when the solvent in solvolysis is water
Term
For solvolysis reactions, the order of reactivity of a substrate is _____ from that found under SN2 reactions
Definition
reversed
Term
In solvolysis reactions, what is the order of reactivity of primary, secondary, and tertiary halides?
Definition
tertiary > secondary > primary
Term
Solvolysis reactions follow a _____ rate law
Definition
first order
Term
Are solvolysis reactions stereospecific?
Definition
no
Term
The rate of the SN2 reaction is proportional to the concentration of _____
Definition
the substrate and the nucleophile
Term
The rate of solvolysis is proportional to the concentration of _____
Definition
the substrate ONLY
Term
unimolecular nucleophilic substitution (AKA SN1)
Definition
solvolysis; only 1 molecule participates in the rate-determining step
Term
Does the rate of an SN1 reaction depend on the concentration of the nucleophile?
Definition
no
Term
carbocation
Definition
a hydrocarbon that contains a positively charged central carbon atom attached to three other groups and bearing only an electron sextet
Term
alkyloxonium ion
Definition
the conjugate acid of an alcohol; when the carbocation is bonded to by water
Term
Why can tertiary halides not undergo SN2 reactions?
Definition
they are to Sterically bulky
Term
SN1 or SN2 mechanism?: tertiary halides
Definition
almost exclusively SN1
Term
SN1 or SN2 mechanism?: primary haloalkanes
Definition
only by SN2
Term
SN1 or SN2 mechanism?: secondary haloalkanes
Definition
either route; depends on conditions
Term
Carbocation stability is linked with _____
Definition
hyperconjugation
Term
For secondary haloalkanes, if we use a substrate carrying a very good leaving group, a poor nucleophile, and a polar protic solvent, then _____ substitution is favored
Definition
unimolecular
Term
For a secondary haloalkane, if we employ a high concentration of a good nucleophile, a polar aprotic solvent, and a haloalkane bearing a reasonable leaving group, than _____ substitution predominates
Definition
bimolecular
Term
2 conditions that must be satisfied before dissociation of a carbon-halogen bond into ions can occur
Definition
1. the carbon atom must be secondary or tertiary so that the carbocation has sufficient thermodynamic stability to form
2. the reaction must take place in a polar solvent capable or interacting with & stabilizing both positive & negative ions
Term
What is meant by saying that the SN2 process is "stereospecific"?
Definition
reaction of a single stereoisomeric substrate gives a single stereoisomeric product
Term
In contrast with SN2 reactions, virtually all reactions that proceed via the SN1 mechanism at a stereocenter give _____
Definition
mixtures of stereoisomers
Term
elimination/E
Definition
starting from a haloalkane, the removal of HX with the simultaneous generation of a double bond
Term
E1
Definition
unimolecular elimination reactions
Term
E1 rate depends on the concentration of _____
Definition
only the starting halide
Term
The rate-determining step in the E1 process is the same as that in _____ reactions
Definition
SN1
Term
What is the rate-determining step in E1 reactions?
Definition
dissociation to a carbocation
Term
In E1 reactions, what is the second step of the mechanism (comes right after dissociation to a carbocation)?
Definition
loss of a proton from a carbon adjacent to the one bearing the positive charge
Term
Any hydrogen positioned on _____ can participate in the E1 reaction
Definition
any carbon next to the center bearing the leaving group
Term
Which is the major product and which is the minor product when E1 and SN1 reactions are both possible?
Definition
major: SN1
minor: E1
Term
SN1, SN2, E1, or E2: good but weakly basic nucleophiles
Definition
SN2 with primary and secondary halides, SN1 with tertiary substrates
Term
SN1, SN2, E1, or E2: weak nucleophiles
Definition
SN1 but react with only secondary & tertiary halides (E1 is minor side reaction)
Term
SN1, SN2, E1, or E2: branched primary substrates
Definition
equal amounts of SN2 and E2
Term
SN1, SN2, E1, or E2: branched secondary substrates
Definition
E2
Term
SN1, SN2, E1, or E2: tertiary halide, neutral/weakly basic conditions
Definition
SN1 and E1
Term
SN1, SN2, E1, or E2: tertiary halide, strong base
Definition
E2
Term
SN1, SN2, E1, or E2: methyl, poor nucleophile
Definition
no reaction
Term
SN1, SN2, E1, or E2: methyl, any decent nucleophile
Definition
SN2
Term
SN1, SN2, E1, or E2: primary substrate, poor nucleophile
Definition
no reaction
Term
SN1, SN2, E1, or E2: primary substrate, good nucleophile
Definition
SN2
Term
SN1, SN2, E1, or E2: primary substrate, hindered nucleophile
Definition
E2
Term
SN1, SN2, E1, or E2: branched primary substrate, poor nucleophile
Definition
no reaction
Term
SN1, SN2, E1, or E2: branched primary substrate, weakly basic
Definition
SN2
Term
SN1, SN2, E1, or E2: branched primary substrate, strongly basic
Definition
E2
Term
SN1, SN2, E1, or E2: secondary substrate, poor nucleophile
Definition
SN1/E1
Term
SN1, SN2, E1, or E2: secondary substrate, weakly basic
Definition
SN2
Term
SN1, SN2, E1, or E2: secondary substrate, strongly basic
Definition
E2
Term
SN1, SN2, E1, or E2: tertiary substrate, poor nucleophile
Definition
SN1/E1
Term
SN1, SN2, E1, or E2: tertiary substrate, weakly basic
Definition
SN1/E1
Term
SN1, SN2, E1, or E2: tertiary substrate, strongly basic
Definition
E2
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