ACIDS 1

in acids and bases what does their ability to donate/ accept electrons effect

their ability to ionise

this effect their lipophilicity which effects their ability to be absorbed/ distributed

lewis acid

accepts a pair of electrons

lewis base

donates a pair of electrons

bronstead acid

proton donor

bronstead base

proton acceptor

what does Ka measure

measures where the equilibrium lies

large Ka

lies to the right

more dissociation -> stronger acid

small Ka

lies to the left

less dissociation -> weaker acid

pKa equation

pKa = -logKa

what is the relationship between pKa and Ka

what does this mean in terms of acids

pKa is inversely proportional to Ka

so if Ka is high pKa is low

low pKa = strong acid

high pKa = weak acid

what is a strong acid in terms of its conjugate base

conjugate base is stable - doesn't react with H+

doesn't reform acid

what is a weak acid in terms of its conjugate base

conjugate base is not stable - reacts with H+

reforms acid

what are the five factors which influence acidity

CARIO

Charge

Atom - size and electronegativity

Resonance

Induction

Orbitals

what does a more positive charge mean

more acidic

what does a more negative charge mean

more basic

how should you determine which molecule is more acidic based on charge

write acid dissociation for each - take off H+ and show conjugate base

remember only proton is lost, electrons collapse

determine charge of CB

no matter the charge (pos or neg) it is always a burden and will always make the molecule unstable

how do you then determine which is more acidic based on charge

more charge = more unstable = weak

less charge = more stable = strong

how do you compare acids when looking at the atom

same period = electronegativity

same group = size

what does it mean to be electronegativity

what does this mean then for acids

if a molecule is electronegative it wants electrons

once it gets them it is stable

how do you determine which molecule is more acidic based on electronegativity

the more electronegative the atom is which is holding the proton the more stable it will be when the proton is lost

SO more electroneg = stronger acid

how do you determine which molecule is more acidic based on atom size

the bigger the atom holding the H is the more stable it will be because neg charge it obtains is more distributed

SO bigger = stronger acid

how does resonance determine acidity of a molecule

more resonance = more stability

this is because it is able to share the neg charge

SO more resonance = stronger acid

two factors to consider when determining effects of induction on acidity

electronegativity

proximity

electronegativity

the more electronegative the stronger the effect -> more stable -> STRONGER ACID

proximity

the closer it is to the atom holding the H the more effect it will have

-> more stabilizing -> STRONGER ACID

how to determine effect of orbitals on acidity

- need to determine if it is sp3,sp2 or sp hybridized

- triple bond = sp

- double bond = sp2

- single bond = sp3

MORE S = MORE STABILITY

trend for acidity in orbitals

sp - most acidic

sp3 - least acidic

how to determine effect of orbitals when given 2 ring systems

- one contains resonance other does not

if resonance is present it hybridizes to sp2 -> more acidic