OCHEM 237 Chapter 3

The Curved-Arrow Notation, Resonance, Acids and Bases, and Chemical Equilibrium

electron-deficient

________ compounds have atoms that are short of an octet of electrons

acids

electron-deficient compounds are ____ because they have more protons than electrons

acids

more protons are what gives ____ their sour taste

water

a proton in water ends up on the ___ molecule because it acts as a base

Lewis acid

the electron-deficient compound in a Lewis Acid-Base Association Reaction is the ___ ___

Lewis base

the compound that donates the electron pair in a Lewis Acid-Base Association Reaction is the __ __

Lewis base, Lewis acid

curve-arrow notation indicates a “flow” of electrons from the electron donor (______)__ to the electron acceptor __(_______) to form the new bond

rich, poor

“the ___ give to the ___”

conserved

in Lewis Acid-Base Reactions, total charge is ____

net charge

reactants and products must have the same ___ ____

spectator ion

if the net charge is not zero, a ____ __ is assumed but may not be shown

do

the “rich” DO or DO NOT have electrons

do not

the “poor” DO or DO NOT have electrons

association

Lewis Acid-Base ______ reactions combine two compounds

dissociation

Lewis Acid-Base _____ reactions separate one compound into two

deficient

In Electron-Pair Displacement Reactions, not all acceptors are electron-_______

depart, receiving

In Electron-Pair Displacement Reactions, an electron pair must ___ from the atom ____ the electron pair

octet rule

In Electron-Pair Displacement Reactions, the ___ ___ is preserved

two

Electron-Pair Displacement Reactions require ___ curved arrow(s)

nucleophile

a species that donates an electron pair to form a new bond

electrophile

a species that accepts an electron pair from the donator

leaving group

the group that accepts electrons from the breaking bond

nucleophiles

(Nucleophiles OR Electrophiles) are electron-rich and Lewis Bases

electrophiles

(Nucleophiles OR Electrophiles) are electron-poor and Lewis Acids

nucleophilic

the specific atom in a compound that donates the electron pair is the _____ center

electrophilic

the specific atom in a compound that receives the electron pair is the _____ center

condensation

any reaction that releases water

reverse, irreversible

each reaction has a finite, nonzero ___ reaction (but some are so small, like 0.00001, that we say the reaction is essentially ____)

nucleophilic

the _____ electron pair can originate from a bond in addition to an unshared electron pair

electrons, nuclei

resonance structures always differ only by movement of ___; ___ do not move

derive

curved-arrow notation is used to help ____ resonance structures

octet configuration

in determining the importance of resonance contributors, an ___ ____ is always favored over electronegativity status

acids

protons can ONLY be ____ because they don’t have any electrons to give

higher, more

resonance contributors have (higher/lower) energy than the hybrid structure, thus the hybrid structure is (more/less) stable

less

higher energy = ____ stable

more

lower energy = ____ stable

octet rule, electronegativity status, neutrality favored over separate charges

When evaluation relative energies of molecules in order to determine resonance importance, list the three rules in order of most to least important

Bronsted acid

a species that donates a proton (H+)

Bronsted base

a species that accepts a proton

proton

a Bronsted acid-base reaction is an electron-pair displacement reaction where a ______ is the electrophilic center

conjugate base

when a Bronsted acid loses a proton, its ____ ____ is formed

conjugate acid

when a Bronsted base gains a proton, its ____ ____ is formed

amphoteric

compounds that can act as either an acid or a base

water

an example of an amphoteric compound

equilibrium

a state where the entire reaction system is happy

products

when Keq >1, the ____ are favored at equilibrium

reactants

when Keq

big

a sample containing A converts into a (big or small) amount of B at equilibrium when Keq>1

small

a sample containing A converts into a (big or small) amount of B at equilibrium when Keq

neither

when Keq=1, _____ are favored at equilibrium

difference

Keq is related to the standard free energy ____ between products and reactants

more, lower

the compound that is (more or less) stable (higher or lower standard free energy) is favored at equilibrium

less

the more free energy a molecule has, the (more or less) stable it is and vice versa

negative

if B (product) is favored at equilibrium, then ∆G is _____

positive

if A (reactant) is favored at equilibrium, then ∆G is _____

spontaneous, does

when the ∆G is negative, the reaction is ______ (it does/does not happen)

not spontaneous, does not

when the ∆G is positive, the reaction is _______ (it does/does not happen)

if Keq >1, then ∆G__

>0

if Keq

=0

if Keq=1, then ∆G__

proton

the strength of a Bronsted acid is determined by how well it transfers a _____ to a Bronsted base

water

the standard base traditionally used in Bronsted reactions is _____

any Bronsted acid

what is this the equilibrium constant for?

dissociation

each acid has its own unique _____ constant, typically expressed as pKa

dissociation constant

which constant is this?

bigger, smaller

weak acids have a (smaller or bigger) pKa and a (smaller or bigger) Ka

smaller, bigger

strong acids have a (smaller or bigger) pKa and a (smaller or bigger) Ka

10⁻¹⁴, 14

The Ka of water = ___ and its pKa =

high

bases have a (high or low) pH

low

acids have a (high or low) pH

less, more

reactions spontaneously go from (more or less) stable reactants to (more or less) stable products

stronger

more reactive = (weaker/stronger) acid or base = less stable

strongest, strongest

one side of the reaction will have the ___ acid and the ___ base

stable

are high pKas more reactive or stable?

reactive

are low pKas more reactive or stable?

50% dissociated

when pH=pKa, molecule is __ ______

Henderson-Hasselbach, dissociation states of conjugate acid-base pairs

which equation is this? and what does it find?

acidic

when pH < pKa, the compound is in ____ form

basic

when pH > pKa, the compound is in the ____ form

ions

___ tend to be water soluble

neutral organics

___ ___ tend to not be water soluble

less

in order for a compound to be in its acidic form, the pH needs to be (more or less) than the pKa by at least 1 unit

more

in order for a compound to be in its basic form, the pH needs to be (more or less) than the pKa by at least 1 unit

charge effect, element effect, hybridization effect, resonance effect, polar/induction effect

list the 5 major factors in acidic strength from most to least important

more, more

for the charge effect, a positively charged ion is (more/less) acidic than a neutrally charged ion which is (more/>less) acidic than a negatively charged ion

increases

for the element effect, acidity (increases/decreases) the farther right you go on the periodic table

electronegativity

the element effect deals with an element’s ________

increase

for the element effect, acidity tends to (increase/decrease) the farther down you go on the periodic table (not always 100% right)

increases

for the hybridization effect, acidity (increases/decreases) with increasing s character

alkanes, alkenes, alkynes

for the hybridization effect, order alkanes, alkenes, and alkynes in order of least to most acidic

triple

which compound would be most acidic: one made up of single bonds or triple bonds?

always

for the resonance effect, resonance is ____ stabilizing

electronegativity

for the polar/induction effect, acidity increases when you have a neighboring atom with high _______

it happens at a distance

the polar/induction effect is weaker than the element effect because ______

adds,

for the polar/induction effect, the closer an electron-withdrawing group is to the charged atom, the more it ____ stability, increasing the acid’s strength

removes

for the polar/induction effect, the closer an electropositive group is to the charged atom, the more it ____ stability, decreasing the acid’s strength

positively

the term electron-deficient does not mean “_____ charged”

charge delocalization

resonance: when the same charge is delocalized onto multiple atoms

charge separation

resonance: opposite charges are created where there was none to start with

small, large

___ changes in ∆G lead to ___ changes in Keq