ACS Organic Chemistry First
Semester Final Exam Study
Guide Questions and Answers
Which is more stable for an acid: resonance in a ring or resonance with a carbonyl? -
Answer- The carbonyl because of the electron density of O
In an acid, a smaller pKa means more or less acidic? - Answer- More acidic
Racemic mixture - Answer- Equal concentrations of enantiomers
Meso compound - Answer- A molecule with two or more stereocenters, but also
containing an internal mirror plane, meaning the compound is not overall chiral
Conformations vs. Configurations - Answer- Conformations refer to the same molecule
rotated around single bonds, such as chair conformations. Configurations refer to
different stereoisomers wherein conversion from one to another would require the
breaking of bonds.
Is the boiling point of a racemic mixture the same as that of each pure enantiomer? -
Answer- No
Strong bases tend towards what types of reactions? - Answer- SN2 or E2
Rank the stability of carbocations - Answer- Tertiary>Secondary>Primary>Methyl
Greater size = ________ nucleophile - Answer- Stronger
How do allyl or benzyl groups affect the speed of an SN2 reaction? - Answer- Increase
speed
Do phenols undergo substitution reactions? - Answer- No
How does protonation affect epoxide reactions? - Answer- If the oxygen is protonated,
the nucleophile will attack the more substituted carbon
T/F: the H atom in an elimination in a ring must be in the same plane as the leaving
group. - Answer- True
, How do polar protic solvents affect SN1, SN2, E1 and E2 reactions? - Answer- Polar
protic solvents stabilize the carbocations intermediate in SN1 and E1 reactions, and
they do not hinder E2 reactions, but they will block the stereocenter/alpha carbon in
SN2 reactions.
How does size of a molecule affect nucleophilicity in polar protic vs polar aprotic
solvents? - Answer- Larger size in polar protic —> greater nucleophilicity
Smaller size in polar aprotic —> greater nucleophilicity
Do non-polar solvents favor unimolecular or bimolecular mechanisms in substitution
elimination reactions? - Answer- Bimolecular, because the charged leaving group does
not want to leave into a non-polar environment
Does heat favor substitution or elimination? - Answer- Elimination
What is an imine? How is it formed? - Answer- An imine is C=N:-H and it is formed via
attack of a carbonyl carbon by ammonia or a derivative, with loss of water
What is an enamine? How is it formed? - Answer- An enamine is an alkene + a
(substituted, usually) amine. It is formed when an ammonia or derivative attacks a
carbonyl carbon with loss of water. The water then eliminates a H, allowing for formation
of a C=C bond.
What is the first step in acetal formation? - Answer- Protonation of the oxygen
What are the substituents of an acetal? Hemiacetal? - Answer- Acetal: -OR, -OR, -R, -H
Hemiacetal: -OR, -OH, -R, -H
Can ethers be hydrolyzed in mildly acidic conditions? - Answer- No
Can NaBH4 reduce carboxylic acids/esters? - Answer- No
Weaker bases lead to more 1,4 or 1,2 additions in vinyl ketones? - Answer- 1,4
Is a N with three different groups chiral? Why or why not? - Answer- No; the lone pair
can flip sides so readily that the molecule does not retain stereochemistry.
How do organocuprates react with carbonyl carbons? Alkenes? - Answer-
Organocuprates react with alkenes, but not with carbonyl carbons.
When are chromium agents used for oxidation? Manganese agents? - Answer-
Chromium in acidic conditions, manganese in basic conditions
What types of chromium agents partially oxidize? Give examples. How is this different
from other chromium agents? - Answer- Anhydrous chromium agents such as PCC.
Other chromium agents fully oxidize.
Semester Final Exam Study
Guide Questions and Answers
Which is more stable for an acid: resonance in a ring or resonance with a carbonyl? -
Answer- The carbonyl because of the electron density of O
In an acid, a smaller pKa means more or less acidic? - Answer- More acidic
Racemic mixture - Answer- Equal concentrations of enantiomers
Meso compound - Answer- A molecule with two or more stereocenters, but also
containing an internal mirror plane, meaning the compound is not overall chiral
Conformations vs. Configurations - Answer- Conformations refer to the same molecule
rotated around single bonds, such as chair conformations. Configurations refer to
different stereoisomers wherein conversion from one to another would require the
breaking of bonds.
Is the boiling point of a racemic mixture the same as that of each pure enantiomer? -
Answer- No
Strong bases tend towards what types of reactions? - Answer- SN2 or E2
Rank the stability of carbocations - Answer- Tertiary>Secondary>Primary>Methyl
Greater size = ________ nucleophile - Answer- Stronger
How do allyl or benzyl groups affect the speed of an SN2 reaction? - Answer- Increase
speed
Do phenols undergo substitution reactions? - Answer- No
How does protonation affect epoxide reactions? - Answer- If the oxygen is protonated,
the nucleophile will attack the more substituted carbon
T/F: the H atom in an elimination in a ring must be in the same plane as the leaving
group. - Answer- True
, How do polar protic solvents affect SN1, SN2, E1 and E2 reactions? - Answer- Polar
protic solvents stabilize the carbocations intermediate in SN1 and E1 reactions, and
they do not hinder E2 reactions, but they will block the stereocenter/alpha carbon in
SN2 reactions.
How does size of a molecule affect nucleophilicity in polar protic vs polar aprotic
solvents? - Answer- Larger size in polar protic —> greater nucleophilicity
Smaller size in polar aprotic —> greater nucleophilicity
Do non-polar solvents favor unimolecular or bimolecular mechanisms in substitution
elimination reactions? - Answer- Bimolecular, because the charged leaving group does
not want to leave into a non-polar environment
Does heat favor substitution or elimination? - Answer- Elimination
What is an imine? How is it formed? - Answer- An imine is C=N:-H and it is formed via
attack of a carbonyl carbon by ammonia or a derivative, with loss of water
What is an enamine? How is it formed? - Answer- An enamine is an alkene + a
(substituted, usually) amine. It is formed when an ammonia or derivative attacks a
carbonyl carbon with loss of water. The water then eliminates a H, allowing for formation
of a C=C bond.
What is the first step in acetal formation? - Answer- Protonation of the oxygen
What are the substituents of an acetal? Hemiacetal? - Answer- Acetal: -OR, -OR, -R, -H
Hemiacetal: -OR, -OH, -R, -H
Can ethers be hydrolyzed in mildly acidic conditions? - Answer- No
Can NaBH4 reduce carboxylic acids/esters? - Answer- No
Weaker bases lead to more 1,4 or 1,2 additions in vinyl ketones? - Answer- 1,4
Is a N with three different groups chiral? Why or why not? - Answer- No; the lone pair
can flip sides so readily that the molecule does not retain stereochemistry.
How do organocuprates react with carbonyl carbons? Alkenes? - Answer-
Organocuprates react with alkenes, but not with carbonyl carbons.
When are chromium agents used for oxidation? Manganese agents? - Answer-
Chromium in acidic conditions, manganese in basic conditions
What types of chromium agents partially oxidize? Give examples. How is this different
from other chromium agents? - Answer- Anhydrous chromium agents such as PCC.
Other chromium agents fully oxidize.
