L3-Acids and Bases
L4-Alkanes and cycloalkanes
=========================================================
Last Name: ID:
1) The compound phenol is shown below. Provide the structure of the conjugate base of phenol.
Answer:
Diff: 2
2) Rank the following compounds in order of acidity.
Answer:
Diff: 3
3) Which sequence correctly ranks the following protons in order of increasing acidity?
4) Which is more acidic, methanesulfonic acid (CH3SO3H) or propanoic acid (CH3CH2CO2H)?
Explain.
Answer: Methansulfonic acid is considerably more acidic. The methanesulfonate ion is much more
stable than the propanoate ion. Both of these conjugate bases are stabilized by resonance
delocalization of the negative charge, but this delocalization is more extensive in the sulfonate.
Diff: 3
5) Consider the species CH3O-, NH2-, and CH3COO-. Rank these ions in order of increasing basicity,
and explain your rationale.
1
, Answer: CH3COO- < CH3O- < NH2-
The first factor to consider is the nature of the atom which bears the negative charge. The more
electronegative the atom that bears the negative charge, the more stable the anion. Stable anions are
less reactive and are hence weaker bases. Since O is more electronegative than N, the NH2- is the
strongest base in the set. In the remaining two species, the negative charge is on the O, but in the
case of CH3COO-, the negative charge is also delocalized by resonance.
Diff: 3
6) Would you predict trifluoromethanesulfonic acid, CF3SO3H, to be a stronger or weaker acid than
methanesulfonic acid, CH3SO3H? Explain your reasoning.
Answer: Trifluoromethanesulfonic acid is a stronger acid. Compare the strengths of the conjugate
bases and remember that the weaker the base, the stronger the conjugate acid. Both bases are
stabilized by resonance, but in the case of the trifluoro derivative, the presence of the highly
electronegative fluorine atoms serves to delocalize the negative charge to an even greater extent due
to the inductive effect. This additional delocalization makes trifluoromethanesulfonate a weaker base.
Diff: 3
7) Provide the name of the compound below.
Answer: 2,3,6,7-tetramethylnonane
Diff: 1
7) Provide an acceptable name for the following compound.
Answer: 4,4-dichloro-6-isopropyl-3-methylnonane
Diff: 2
8) Provide the IUPAC name of (CH3)2CHCH2CH2C(CH3)3.
Answer: 2,2,5-trimethylhexane
Diff: 2
9) Draw an acceptable structure for 6-ethyl-2,6,7-trimethyl-5-propylnonane.
Answer:
2
L4-Alkanes and cycloalkanes
=========================================================
Last Name: ID:
1) The compound phenol is shown below. Provide the structure of the conjugate base of phenol.
Answer:
Diff: 2
2) Rank the following compounds in order of acidity.
Answer:
Diff: 3
3) Which sequence correctly ranks the following protons in order of increasing acidity?
4) Which is more acidic, methanesulfonic acid (CH3SO3H) or propanoic acid (CH3CH2CO2H)?
Explain.
Answer: Methansulfonic acid is considerably more acidic. The methanesulfonate ion is much more
stable than the propanoate ion. Both of these conjugate bases are stabilized by resonance
delocalization of the negative charge, but this delocalization is more extensive in the sulfonate.
Diff: 3
5) Consider the species CH3O-, NH2-, and CH3COO-. Rank these ions in order of increasing basicity,
and explain your rationale.
1
, Answer: CH3COO- < CH3O- < NH2-
The first factor to consider is the nature of the atom which bears the negative charge. The more
electronegative the atom that bears the negative charge, the more stable the anion. Stable anions are
less reactive and are hence weaker bases. Since O is more electronegative than N, the NH2- is the
strongest base in the set. In the remaining two species, the negative charge is on the O, but in the
case of CH3COO-, the negative charge is also delocalized by resonance.
Diff: 3
6) Would you predict trifluoromethanesulfonic acid, CF3SO3H, to be a stronger or weaker acid than
methanesulfonic acid, CH3SO3H? Explain your reasoning.
Answer: Trifluoromethanesulfonic acid is a stronger acid. Compare the strengths of the conjugate
bases and remember that the weaker the base, the stronger the conjugate acid. Both bases are
stabilized by resonance, but in the case of the trifluoro derivative, the presence of the highly
electronegative fluorine atoms serves to delocalize the negative charge to an even greater extent due
to the inductive effect. This additional delocalization makes trifluoromethanesulfonate a weaker base.
Diff: 3
7) Provide the name of the compound below.
Answer: 2,3,6,7-tetramethylnonane
Diff: 1
7) Provide an acceptable name for the following compound.
Answer: 4,4-dichloro-6-isopropyl-3-methylnonane
Diff: 2
8) Provide the IUPAC name of (CH3)2CHCH2CH2C(CH3)3.
Answer: 2,2,5-trimethylhexane
Diff: 2
9) Draw an acceptable structure for 6-ethyl-2,6,7-trimethyl-5-propylnonane.
Answer:
2
