Orgo Chem Quiz #6

acids

donate protons

bases

accept protons

conjugate acid

when a base accepts protons

conjugate base

when an acid gives protons

electron movement

making and breaking bonds

curved arrows

describe flow of electron density + physical movement of electrons

same as resonance structures

flow of electron density

1. base “attacks” acid using electron pair

2. acid cannot lose its proton without base taking it

3. shows 2 arrows indicating two pairs of electrons move simultaneously, 1 showing the breaking of the bond and the other showing the building of the bond

pKa

quantitative strength

Ka

acid dissociation constant of an acid dissolved in water

measures acid’s strength when water is a base

Keq

[H3O+] [A-] / [HA] [H20]

Ka

[H3O+] [A-] / [HA]

stronger acid

Ka > 1 

weaker acid

Ka < 1

pKa

-log of Ka

stronger acid

lower pKa

weaker acid

higher pKa

order of magnitude

unit of pKa represents this

ex. HBr (pKa = -9) is 10 times stronger acid than HCl (pKa = -8)

weaker

stronger the acid, the _______ its conjugate base is

equilibrium

favors weaker acid + weaker base

products

reactants

subtracting pKa values tells you 10x times more ________ than ________

stability of conjugate bases

without pKa values, we have to evaluate __________

stable

stronger the acid —> more _____ the conjugate base

conjugate base

when acid loses proton, ____________ is formed which contains lone pair of electrons

lone pair

the stability of the conjugate base compares to the stability of the __________

more effectively a conjugate base can stabilize its negative charge/lone pair, the ______ the acid

factors that affect negative charge stability (ARIO) 

type of atom

resonance

inductive effects

type of orbital

type of atom

stable

the larger and more electronegative the atom is, the more _____ the conjugate base

stable

the shorter the atomic orbital is, the closer the atom is to the nucleus

the closer the electrons are to the nucleus, the more ____ they are

resonance

inductive effects

stable

more electron jobs, more ______ conjugate base

stable

closer the electron withdrawing groups to negative charge, more _____ conjugate base

type of orbital

stable

more s-character, more _____ the negative charge

lewis acid

accepts pair of electrons

lewis base

donates pair of electrons

lewis acids and bases

acids under Bronsted-Lowry definitions are also considered _______

bronsted-lowry and lewis acids and bases

ONLY lewis definitions

lewis definitions

conjugate acids and bases are not produced since it creates one product

amino acids

contain amino group and carboxylic acid group

form zwitterons (number of positive and negatively charged functional groups) at physiological pH

heat energy

exchange between reaction and surroundings

breaking bonds

system absorbs energy

bond

electrons that absorb kinetic energy to overcome stability of ____

how bonds can break

heterolytically and homolytically

homolytically

produce radicals

heterolytically

produces ions

bond dissociation energy (BDE) 

homolytic bond cleavage

when bonds break or form

exothermic

energy gained by bonds formed exceeds energy needed for bonds to be broken

products are more stable that reactants

endothermic

energy needed for bonds broken exceeds stability gained by bonds formed

products are less stable than reactants

energy diagram

describes kinetics and thermodynamics of reaction

potential energy = y-axis

reaction progress = x-axis

enthalpy (△H)

BDE (bonds broken) - BDE (bonds formed) 

entropy

molecular disorder, randomness, or freedom

number of vibrational, rational, and translational states among which the energy of compound is distributed

number of states the molecules spread across increases with increasing volume

enthalpy (△H)

total heat content of system

entropy (△S)

more volume for gas to occupy, ______ entropy

spontaneous

if total entropy is positive, reaction is _______

positive

spontaneous

if there are more moles of product than reactants, system entropy will be ______ and reaction will be ________

spontaneous

positive

if cyclic compound becomes acyclic, reaction will be ______ and system entropy will be _______

spontaneous 

exergonic

if △G is negative, reaction is _____ and _______

nonspontaneous

endergonic

if △G is positive, reaction is ______ and _______

△H

change in enthalpy of surroundings

△S

change in entropy of system

Gibb’s free energy (△G)

△H - T△S

products

△G is negative, ______ are favored

reaction rate

function of number of molecular collisions that will occur in a given period of time

reaction rate factors

reactant concentration

activation energy

temperature

geometry and sterics

presence of catalyst

rate law

k[reactants]

rate constant

k

reactant concentration

[reactants]

rate order

represented by x + y variables

first order

rate = k[A]

second order

rate = [A][B]

third order

rate = [A]²[B]

activation energy

energy barrier between reactants and products

minimum amount of energy required for molecular collision to result in reaction

decreases

as activation energy increases, the number of molecules possessing enough energy to react ______

higher

lower activation energy means _____ reaction rate

faster

raising temperature will result in a _____ reaction

more

At higher T, molecules have ____ kinetic energy and ____ molecules will have enough energy to produce reaction

steric considerations

steric hindrance and geometry of compound affect rate of reaction

orientation

when molecules collide, they must have correct ________ for bonds to made/broken

low

if reactive conformation of compound is high energy, it will spend less time in that conformation, so the probability of collision resulting in reaction is ___

catalysts

speed up reactions without consumption 

ex. enzymes

lowers activation energy

kinetics

____ = reaction rate

thermodynamics

_______ = equilibrium

kinetically favored products

lower activation energy and products are lower in energy, form faster, and are more stable

higher activation energy

higher activation energy and products are higher in energy, form slower, and are less stable

transition state

high-energy state a reaction passes through

energy maxima → represent the transition as bonds being made and broken

not observable

intermediate

species during reaction

exist for period of time

observable

2 points on diagram that are close in energy

similar structure 

can generalize the structure of transition state depending on if reaction is exo- or endothermic

exothermic reaction

transition state resembles reactants on diagram

endothermic reaction

transition states resemble products on diagram

polar reactions

involve ions as reactants, intermediates, and/or products

negative attracts positive

electron-rich species attract electron-deficient species

nucleophile

electron-rich, donate electron pairs

lewis base

nucleophile

more polarizable, the stronger the _______

electrophile

electron-deficient species, accept electron pairs

lewis acid

ex. carbocations and partially positive atoms

curved arrows

show how electrons move as bonds break and form

patterns of polar reactions

nucleophilic attack

loss of leaving group 

proton transfer

rearrangements

nucleophilic attack

nucleophile attacking an electrophile

tail of arrow starts at negative charge

head of arrow ends on positive charge

electrons end up being shared rather than transferred

may need more than 1 arrow

nucleophile

pi bonds act as _______