OChem 241 Chapter 2 Part 2
strong organic acid
p-toluenesulfonic acid (TsOH)
Bronsted-Lowry base
proton acceptor
A lone pair on a _____ hybridized atom will be lower in energy (i.e. more stable) than a lone pair on a _____ hybridized atom.
sp; sp2 sp2; sp3 sp; sp3
A
stabilized by induction
Which statement(s) correctly describe(s) aspirin, and the proton transfer reaction that converts aspirin to its conjugate base (shown)?
If NaOH was used as the base, then the ionic form of aspirin would be favored at equilibrium. Aspirin is a weak acid.
Which of the following statements correctly describe the effect of the presence of more electronegative atoms on acidity? (Select all that apply.)
In an acid H-A, electronegative atoms attached to A stabilize the conjugate base by induction. The acidity of an acid H-A increases if there are more electronegative atoms attached to element A.
H2O
Lewis and Bronsted-Lowry acid
Select all statements that correctly describe Lewis and Bronsted-Lowry acids and bases.
Not all Lewis acids are Bronsted-Lowry acids. All Bronsted-Lowry acids are Lewis acids.
Rank the following compounds in order of increasing acidity using the periodic table. Place the least acidic compound at the top of the list and the most acidic compound at the bottom of the list.
SiH4 PH3 H2S
When comparing the acidity of two acids (for example, H-A and H-B), which of the following should be considered FIRST?
The acidity of H-A and H-B based on the location of A and B in the periodic table
Which of the following statements describes a Lewis acid-base reaction correctly?
The base donates an electron pair to the acid.
Which of the following statements correctly describes the process that occurs in a Lewis acid-base reaction?
The base uses its electron pair to form a new covalent bond to the acid.
Why does the acidity of an acid, general formula H-A, increase from left to right across a period?
The electronegativity of element A increases across a period.
For a base of formula A:-, as the s character of the orbital containing the lone pair increases, the stability of the base _____ and the strength of its conjugate acid HA _____.
increases, increases
The pull of electron density through σ bonds is called the ____ effect and is caused by a difference in the ____of the atoms involved.
inductive electronegativity
Which of the following are commonly used as bases in organic reactions? (Select all that apply.)
lithium diisopropylamide butyllithium -OH and its organic derivatives triethylamine
The structure of p-toluenesulfonic acid most closly resembles the structure of _____.
H2SO4
strong inorganic acid
HCl
HI is a stronger acid than HCl, HBr, or HF. This is because _____.
I is larger than F, Cl, or Br.
Which of the following statements correctly describes the relationship between negative character and basic strength?
A negative charge does not necessarily make a species a strong base.
Which of the following species are common negatively charged strong bases? Select all that apply.
-NH2 -OH -H
Which of the following conjugate bases are stabilized by resonance? (Select all that apply.)
A C
Rank the following compounds based on decreasing acid strength. Place the strongest acid at the top of the list and the weakest acid at the bottom of the list
A C B
Without using a Ka or pKa table, rank the three compounds shown based on increasing acidity. Place the least acidic molecule at the top of the list
A C B
Rank the following compounds in order of increasing acidity. Place the least acidic compound at the top of the list and the most acidic compound at the bottom of the list.
A D C B
What is the MOST important factor in determining the acidity of acids H-A, where elements A are in the same group of the periodic table?
The size of A
Rank the following compounds in order of increasing acidity using the periodic table. Place the least acidic compound at the top of the list and the most acidic compound at the bottom of the list.
H2O HF HBr
strong organic base
CH3CH2CH2CH2-Li+ (butyllithium)
BF3
Lewis acid
Which of the following statements correctly describe periodic trends in the acidity of an acid with the general formula HA? (Select all that apply.)
Acidity of HA increases as atom A moves down a group. Acidity of HA increases as atom A moves from left to right across a period.
Which of the following species commonly act as Lewis acids in organic reactions? (Select all that apply.)
AlCl3 BF3
Consider the Lewis acid-base reaction shown. Which of the following statements correctly describes the curved arrow mechanism for this transformation?
An arrow must begin on a lone pair on Cl— and end on the B atom.
Which of the following statements correctly describe the curved arrows needed to show the mechanism for the Lewis acid-base reaction shown? (Select all that apply.)
An arrow must begin on a lone pair on the O of -OH and end on the carbonyl C atom. An arrow must begin on the π bond of the C=O and end on the carbonyl O atom.
Select all statements that correctly describe the acid-base chemistry of aspirin and its biological implications.
Aspirin contains a carboxylic acid functional group. In the basic environment of the small intestine, aspirin is deprotonated to form its conjugate base.
Select the correct structure of the product formed by the Lewis acid-base reaction between BCl3 and CH3OH.
B
Rank the following compounds according to increasing acidity. Place the weakest acid at the top of the list and the strongest acid at the bottom of the list.
B C A
Rank the following molecules in order of decreasing pKa value. The molecule with the largest pKa value should be placed at the top of the list and the molecule with the smallest pKa value at the bottom of the list
B C A
Without using a Ka or pKa table, rank the three compounds shown based on decreasing acidity. Place the most acidic molecule at the top of the list
C B A
Select the structure of the product formed by the Lewis-acid base reaction between chloride anion (Cl-) and the carbocation CH3CH+CH+CH3
CH3CH(Cl)CH3
Which of the following acids have a conjugate base stabilized by resonance? (Select all that apply.)
ClCH2COOH CH3CH2CN
True or false: Since bases require an available lone pair, any species with a negative charge is a strong base.
False
Which of the following is the MOST important factor that determines the acidity of an H-A bond?
The location of element A in the periodic table
Select all statements that correctly relate the acidity of an organic molecule to the presence of electronegative atoms within the molecule.
The pKa of an acidic molecule will decrease if a Cl atom in the molecule is replaced by F. The acidity increases as electronegative atoms are brought closer to the acidic site.
Which of the following statements correctly describe the inductive effect? (Select all that apply.)
This effect is the result of electronegativity differences between atoms. Inductive effects operate through σ bonds.
A Lewis acid is an electron pair _____, while a Lewis base is an electron pair _____.
acceptor, donor
In the reaction shown, the -OH ion is the Lewis _____ and the _____ while the cation (CH3)2CH+ is the Lewis _____ and the _____.
base; nucleophile; acid; electrophile
A base such as the acetate anion (shown) exists as a resonance hybrid, which means that electrons are ____ over several atoms. Such a structure is stabilized by ____ and is therefore a ____ base than one with a localized charge.
delocalized resonance weaker
In a Lewis acid-base reaction, the base _____ an electron pair to/from the acid. This is an example of a general reaction trend, i.e., that electron-rich species react with electron-_____ species.
donates, deficient
In a Lewis acid-base reaction, the base donates a(n) ___pair to form a new ___bond between the base and the acid.
electron covalent
Lewis acid
electron pair acceptor
Lewis base
electron pair donor
electrophile
electron-poor species
nucleophile
electron-rich species
The presence of more electronegative atoms in a compound _____ its acidity by the inductive effect.
increases
The acidity of acid H-A ____as atom A moves from left to right across a period and ____ down a group in the periodic table.
increases increases
The presence of electronegative atoms in an organic molecule increase the acidity by induction. The effect increases as the electronegativity of the atom _____ and the electronegative atom is _____ the site of the acidic proton.
increases, closer to
An electron pair in an sp hybridized orbital is at a _____ energy than an electron pair in an sp2 hybridized orbital. A conjugate base A- that has its lone pair located in an sp2 hybridized orbital is therefore _____ stable than a base that has its lone pair located in an sp hybridized orbital.
lower, less
A species that is nucleus loving is known as a ____, whereas a compound that is electron loving is known as an ____
nucleophile electrophile
Bronsted-Lowry acid
proton donor
weak organic base
pyridine
Which type of stabilization has a greater effect on the pKa value of an acid: induction or resonance?
resonance
Consider a conjugate base of the general formula A-. Rank the conjugate base in order of decreasing stability in terms of the hybrid orbital in which the lone pair of A- is located. Place the most stable situation at the top of the list and the least stable situation at the bottom of the list
sp sp2 sp3
B
stabilized by resonance
Which of the following statements correctly explains how the conjugate base of an acid may be resonance stabilized?
the neg
The name of the compound shown is ___acid, which is often abbreviated as ____
tosylic TsOH
Acetic acid (CH3COOH) is a ____ acid than glycolic acid (HOCH2COOH) because the acetate anion is ____stable than the glycolate anion.
weaker less
H2S is a _____ acid than HCl because S is _____ electronegative than Cl and therefore the conjugate base HS- is _____ able to stabilize a negative charge than the conjugate base Cl-.
weaker, less, less
Inductive effects refer to the pull of electrons through _____ bonds, while resonance effects operate by delocalization of electrons through _____ bonds.
σ, π
