CHEM 109B MIDTERM 1 EXAM WITH COMPLETE SOLUTIONS 100%
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Effects of sterics on the rate of a SN2 reaction - (ANSWER)Rate decreases as steric hindrance increases
What kind of alkyl halides undergo SN2 - (ANSWER)Methyl, primary, and secondary
What makes a good leaving group (aprotic) - (ANSWER)A weak (stable) base
What is the configuration of products in SN2 - (ANSWER)Inverted product only
What is the configuration of products in SN1 - (ANSWER)Inverted and retained configurations
What is the effect of a strong Nu- on the rate of SN1 and SN2 - (ANSWER)a strong Nu- has no effect on
SN1 because it does not take part in the rate determining step.
A strong Nu- increases the rate of reaction in SN2
What is the general mechanism of an E2 reaction like - (ANSWER)ALL ONE STEP
- a strong base removes a H from a beta-carbon
- the e- from the previous H-C bond form a double bond between the alpha and beta carbon
- the leaving group leaves
Dehydrohalogenation - (ANSWER)Removal of a proton and halide ion
Alpha-carbon: - (ANSWER)The carbon to which the halogen is attached
Beta-carbon - (ANSWER)The carbon(s) adjacent to the alpha-carbon from which a H will be removed in a
elimination reaction
What is an elimination reaction initiated by - (ANSWER)The removal of a proton from a beta-carbon
,CHEM 109B MIDTERM 1 EXAM WITH COMPLETE SOLUTIONS 100%
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Which beta-carbon in an E2 reaction is a hydrogen usually eliminated from - (ANSWER)The beta-carbon
that is bonded to the fewest hydrogens
Which beta-carbon in an E2 reaction is a hydrogen usually eliminated if the reaction has a bulky base and
if its approach to the alkyl halide is sterically hindered and why - (ANSWER)A hydrogen will be removed
from the beta-carbon who's hydrogen are most easily accessible because of steric hindrance, usually the
more unstable alkene will be formed
What happens in an E2 reaction that begins with an alkyl fluoride? Why? - (ANSWER)The less stable
alkene will be formed because F is a poor leaving group. As H is removed, F is slower to leave so it will
remove the H that is further away from it, usually from the Beta-carbon with more H
What are carbocations stabilized by - (ANSWER)Stabilized by hyperconjugation and e- donating alkyl
groups
Relative reactivity of alkyl halides in E2 - (ANSWER)3 > 2 > 1
What is the general mechanism of an E1 reaction - (ANSWER)2 STEPS
1. leaving group leaves and carbocation forms
- carbocation arrangement if possible
2. Relatively weak base removes H from B-carbon and the e- from that bond form a double bond
between the B-carbon and A-carbon
Which alkyl halides undergo only E2 - (ANSWER)Primary and secondary
What elimination reactions do tertiary alkyl halides undergo - (ANSWER)E2 - when there is a strong or
bulky base
E1 - when there is a weak base
, CHEM 109B MIDTERM 1 EXAM WITH COMPLETE SOLUTIONS 100%
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Which elimination reaction requires the L.G and the leaving proton to both be in the anti position -
(ANSWER)E2
What are the products of an E2 reaction in which the proton that is removed is from a b-carbon that
originally had 2 H in the reactants - (ANSWER)Both E and Z are formed
What are the products of an E2 reaction in which the proton that is removed is from a b-carbon that
originally had 1 H in the reactants - (ANSWER)1 stereoisomer formed whose configuration is dependent
on the reactant
What is the stereochemistry of the products of an E1 reaction - (ANSWER)Both E and Z formed but the
major product is the one with the largest groups on opposite sides of the double bond
What has to occur in an E2 reaction of cyclohexanes - (ANSWER)Both groups being removed must be
parallel so both groups must be in axial, even if the b-hydrogen that is being removed didn't have the
most H on it
Relative reactivities of SN2 - (ANSWER)1 > 2 > 3
What kind of product will the reaction of a 1 alkyl halide with a Nu-/base that is not sterically hindered -
(ANSWER)Mostly substitution
Does elimination or substitution occur faster for a secondary alkyl halide with a regular Nu-/base -
(ANSWER)Secondary alkyl halides react faster in E2 than SN2 but both will occur
As the Nu-/base becomes stronger an bulkier in a reaction with a secondary alkyl halide, what happens
to the main products - (ANSWER)A greater yield of the elimination product
What kinds of substitution and elimination reactions occur to tertiary alkyl halides? Which is favored? -
(ANSWER)SN1 and E1, and SN2 but substitution favored because no bonds have to be broken for it to
occur
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Effects of sterics on the rate of a SN2 reaction - (ANSWER)Rate decreases as steric hindrance increases
What kind of alkyl halides undergo SN2 - (ANSWER)Methyl, primary, and secondary
What makes a good leaving group (aprotic) - (ANSWER)A weak (stable) base
What is the configuration of products in SN2 - (ANSWER)Inverted product only
What is the configuration of products in SN1 - (ANSWER)Inverted and retained configurations
What is the effect of a strong Nu- on the rate of SN1 and SN2 - (ANSWER)a strong Nu- has no effect on
SN1 because it does not take part in the rate determining step.
A strong Nu- increases the rate of reaction in SN2
What is the general mechanism of an E2 reaction like - (ANSWER)ALL ONE STEP
- a strong base removes a H from a beta-carbon
- the e- from the previous H-C bond form a double bond between the alpha and beta carbon
- the leaving group leaves
Dehydrohalogenation - (ANSWER)Removal of a proton and halide ion
Alpha-carbon: - (ANSWER)The carbon to which the halogen is attached
Beta-carbon - (ANSWER)The carbon(s) adjacent to the alpha-carbon from which a H will be removed in a
elimination reaction
What is an elimination reaction initiated by - (ANSWER)The removal of a proton from a beta-carbon
,CHEM 109B MIDTERM 1 EXAM WITH COMPLETE SOLUTIONS 100%
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Which beta-carbon in an E2 reaction is a hydrogen usually eliminated from - (ANSWER)The beta-carbon
that is bonded to the fewest hydrogens
Which beta-carbon in an E2 reaction is a hydrogen usually eliminated if the reaction has a bulky base and
if its approach to the alkyl halide is sterically hindered and why - (ANSWER)A hydrogen will be removed
from the beta-carbon who's hydrogen are most easily accessible because of steric hindrance, usually the
more unstable alkene will be formed
What happens in an E2 reaction that begins with an alkyl fluoride? Why? - (ANSWER)The less stable
alkene will be formed because F is a poor leaving group. As H is removed, F is slower to leave so it will
remove the H that is further away from it, usually from the Beta-carbon with more H
What are carbocations stabilized by - (ANSWER)Stabilized by hyperconjugation and e- donating alkyl
groups
Relative reactivity of alkyl halides in E2 - (ANSWER)3 > 2 > 1
What is the general mechanism of an E1 reaction - (ANSWER)2 STEPS
1. leaving group leaves and carbocation forms
- carbocation arrangement if possible
2. Relatively weak base removes H from B-carbon and the e- from that bond form a double bond
between the B-carbon and A-carbon
Which alkyl halides undergo only E2 - (ANSWER)Primary and secondary
What elimination reactions do tertiary alkyl halides undergo - (ANSWER)E2 - when there is a strong or
bulky base
E1 - when there is a weak base
, CHEM 109B MIDTERM 1 EXAM WITH COMPLETE SOLUTIONS 100%
VERIFIED!!! ALREADY GRADED A+ LATEST UPDATE!!!
Which elimination reaction requires the L.G and the leaving proton to both be in the anti position -
(ANSWER)E2
What are the products of an E2 reaction in which the proton that is removed is from a b-carbon that
originally had 2 H in the reactants - (ANSWER)Both E and Z are formed
What are the products of an E2 reaction in which the proton that is removed is from a b-carbon that
originally had 1 H in the reactants - (ANSWER)1 stereoisomer formed whose configuration is dependent
on the reactant
What is the stereochemistry of the products of an E1 reaction - (ANSWER)Both E and Z formed but the
major product is the one with the largest groups on opposite sides of the double bond
What has to occur in an E2 reaction of cyclohexanes - (ANSWER)Both groups being removed must be
parallel so both groups must be in axial, even if the b-hydrogen that is being removed didn't have the
most H on it
Relative reactivities of SN2 - (ANSWER)1 > 2 > 3
What kind of product will the reaction of a 1 alkyl halide with a Nu-/base that is not sterically hindered -
(ANSWER)Mostly substitution
Does elimination or substitution occur faster for a secondary alkyl halide with a regular Nu-/base -
(ANSWER)Secondary alkyl halides react faster in E2 than SN2 but both will occur
As the Nu-/base becomes stronger an bulkier in a reaction with a secondary alkyl halide, what happens
to the main products - (ANSWER)A greater yield of the elimination product
What kinds of substitution and elimination reactions occur to tertiary alkyl halides? Which is favored? -
(ANSWER)SN1 and E1, and SN2 but substitution favored because no bonds have to be broken for it to
occur
