STRUCTURAL EFFECTS ON ACIDITY pt2

INDUCTIVE EFFECT

Shift in electron density through charge polarization transmitted through

sigma (σ) bonds.

pi

_ bonds are involved in resonance

Electron-withdrawing groups

stabilizes conjugate base

Electron-donating groups

destabilizes conjugate base

-F, -CO2H, (benzene ring), -Cl, -CO2R, (N with + charge and two lines), -Br, -C(=O)-, (S with + charge and two lines), -I, -CN, -OR, -NO2, -OH, -SO2-, -N(with two lines), (two lines with double bond), -SR, (two lines with triple bond), -SH

Electron-withdrawing groups 20

-O-

-CH3

-CO2-

Electron-donating groups 3

Electron-withdrawing groups

Electron attracting

Electron-donating groups

Electron repelling

inductive electron

_withdrawal stabilizes the base

ELECTRON WITHDRAWING SUBSTITUENT

ACIDITY INCREASES AS YOU ADD _

STERIC EFFECT

Results from the presence of bulky groups

STERIC EFFECT

Results to congestion and twisting of bonds

Steric

*_ hindrance rather than inductive effect (AT TIMES)

F (STRONGER EWG, MORE EN TOO) INDUCTIVE EFFECT

2,2- (SUSBTITUENTS ARE NEARER THE ACETIC HYDROGEN)

INDUCTIVE EFFECT

DISTANCE BETWEEN EW AND ACIDIC H DECRESEASES EW EFFECT

FIRST (EWG IS STRONGER)

SECOND (EN)

Which is a stronger acid?

SECOND

Which is a stronger acid?

SECOND

acid

Resonance in the acid stabilizes and weakens the _.

acid

Resonance in the conjugate base stabilizes the conjugate base and strengthens the _.

acidity

Delocalization of charge in the conjugate base anion increases _.

conjugate base anion

Delocalization of charge in the _ increases acidity.

inductive electron

Two factors cause the conjugate base of a carboxylic acid to be more stable than the

conjugate base of an alcohol:

◦ First, _ withdrawal:

pi electron

Two factors cause the conjugate base of a carboxylic acid to be more stable than the

conjugate base of an alcohol:

◦ Second, _ delocalization/resonance:

ACID

IF CB IS UNSTABLE; _ IS VERY WEAK

SECOND (IT HAS 3 RESONANCE FORMS)

ACIDITY

INDUCTIVE EFFECT INCREASES _

HYBRIDIZATION

ELECTRON WITHDRAWING IS VIRTUE WITH ITS _

CANNOT DELOCALIZE WITH AROMATIC RING

hybridization

Inductive effect due to _ INCREASES ACIDITY

ACIDITY

Inductive effect due to hybridization INCREASES _

ACIDITY

Resonance WEAKENS _

ortho

Steric effect due to substituents in the _ position prevents resonance.

resonance

Steric effect due to substituents in the ortho position prevents _.

stability of acid

Decreased resonance decreases _ and INCREASES ACIDITY.

ACIDITY

Decreased resonance decreases stability of acid and INCREASES _.

resonance

Decreased _ decreases stability of acid and INCREASES ACIDITY.

Ortho position

Meta position

Para position

POSITIONS 3

Ortho position

electron-withdrawing effect + steric effect → stabilizes anion,

destabilizes acid and increases acidity

steric effect

Ortho position:

electron-withdrawing effect + _→ stabilizes anion,

destabilizes acid and increases acidity

Electron-withdrawing group on benzoic acid

anion

Ortho position:

electron-withdrawing effect + steric effect → stabilizes _,

destabilizes acid and increases acidity

Electron-withdrawing group on benzoic acid

acid

Ortho position:

electron-withdrawing effect + steric effect → stabilizes anion,

destabilizes _ and increases acidity

Electron-withdrawing group on benzoic acid

acidity

Ortho position:

electron-withdrawing effect + steric effect → stabilizes anion,

destabilizes acid and increases _

Electron-withdrawing group on benzoic acid

Meta position

electron-withdrawing effect → stabilizes anion and increases

acidity

Electron-withdrawing group on benzoic acid

electron-withdrawing effect

Meta position

_ → stabilizes anion and increases

acidity

Electron-withdrawing group on benzoic acid

anion

Meta position

electron-withdrawing effect → stabilizes _ and increases

acidity

Electron-withdrawing group on benzoic acid

acidity

Meta position

electron-withdrawing effect → stabilizes anion and increases

_

Electron-withdrawing group on benzoic acid

Para position

electron-withdrawing effect + resonance → stabilizes anion,

destablilizes unionized acid and increases acidity

Electron-withdrawing group on benzoic acid

electron-withdrawing effect

Para position

_ + resonance → stabilizes anion,

destablilizes unionized acid and increases acidity

Electron-withdrawing group on benzoic acid

resonance

Para position

electron-withdrawing effect + _ → stabilizes anion,

destablilizes unionized acid and increases acidity

Electron-withdrawing group on benzoic acid

anion

Para position

electron-withdrawing effect + resonance → stabilizes _,

destablilizes unionized acid and increases acidity

Electron-withdrawing group on benzoic acid

unionized acid

Para position

electron-withdrawing effect + resonance → stabilizes anion,

destablilizes _ and increases acidity
Electron-withdrawing group on benzoic acid

acidity

Para position

electron-withdrawing effect + resonance → stabilizes anion,

destablilizes unionized acid and increases _

Electron-withdrawing group on benzoic acid

acid

Resonance form of _ is unfavorable – electron-withdrawing group close to a positive charge

Electron-withdrawing group on benzoic acid

positive

Resonance form of acid is unfavorable – electron-withdrawing group close to a _ charge

Electron-withdrawing group on benzoic acid

Electron-withdrawing group on benzoic acid

Resonance form of acid is unfavorable – electron-withdrawing group close to a

positive charge

electron-withdrawing effect

Ortho position

_+ steric effect → stabilizes anion,

destabilizes acid and increases acidity

Electron-withdrawing group on benzoic acid

Ortho position

steric effect > electron-donating effect → destabilizes acid

and increases acidity

Electron-donating group on benzoic acid

steric effect

Ortho position

_ > electron-donating effect → destabilizes acid

and increases acidity

Electron-donating group on benzoic acid

electron-donating effect

Ortho position

steric effect > _ → destabilizes acid

and increases acidity

Electron-donating group on benzoic acid

acid

Ortho position

steric effect > electron-donating effect → destabilizes _

and increases acidity

Electron-donating group on benzoic acid

acidity

Ortho position

steric effect > electron-donating effect → destabilizes acid

and increases _

Electron-donating group on benzoic acid

Meta position

electron-donating effect → destabilizes anion and decreases

acidity

Electron-donating group on benzoic acid

electron-donating effect

Meta position

_ → destabilizes anion and decreases

acidity

Electron-donating group on benzoic acid

anion

Meta position

electron-donating effect → destabilizes _ and decreases

acidity

Electron-donating group on benzoic acid

acidity

Meta position

electron-donating effect → destabilizes anion and decreases

_

Electron-donating group on benzoic acid

Para position

electron-donating effect + resonance → destabilizes anion,

stabilizes acid and decreases acidity

Electron-donating group on benzoic acid

electron-donating effect

Para position

_+ resonance → destabilizes anion,

stabilizes acid and decreases acidity

Electron-donating group on benzoic acid

resonance

Para position

electron-donating effect + _ → destabilizes anion,

stabilizes acid and decreases acidity

Electron-donating group on benzoic acid

anion

Para position

electron-donating effect + resonance → destabilizes _,

stabilizes acid and decreases acidity

Electron-donating group on benzoic acid

acid

Para position

electron-donating effect + resonance → destabilizes anion,

stabilizes _ and decreases acidity

Electron-donating group on benzoic acid

acidity

Para position

electron-donating effect + resonance → destabilizes anion,

stabilizes acid and decreases _

Electron-donating group on benzoic acid

Electron-donating group on benzoic acid

Resonance form of acid is favorable – electron-donating group close to a positive

charge

favorable

Resonance form of acid is _ – electron-donating group close to a positive

Electron-donating group on benzoic acid

Ortho position

– steric effect > resonance effect

Substituents on benzoic acid that can participate in resonance

steric

Ortho position – _ effect > resonance effect

Substituents on benzoic acid that can participate in resonance

resonance

Ortho position – steric effect > _ effect

Substituents on benzoic acid that can participate in resonance

Meta position

– inductive effect (no resonance forms involving carboxyl group)

Substituents on benzoic acid that can participate in resonance

inductive; carboxyl

Meta position – _ effect (no resonance forms involving ——- group)

Substituents on benzoic acid that can participate in resonance

Para position

– resonance effect

Substituents on benzoic acid that can participate in resonance

resonance

Para position – _ effect

Substituents on benzoic acid that can participate in resonance

Ortho position

_ – steric effect

Substituents on benzoic acid that can participate in resonance

steric

Ortho position – _ effect

Substituents on benzoic acid that can participate in resonance

Meta position

_ – inductive effect (no resonance forms involving carboxyl group)

Substituents on benzoic acid that can participate in resonance

carboxyl

Meta position – inductive effect (no resonance forms involving _ group)

Substituents on benzoic acid that can participate in resonance

Para position

_ – resonance effect

Substituents on benzoic acid that can participate in resonance

resonance

Para position – _ effect

Substituents on benzoic acid that can participate in resonance

benzoic acid

Substituents on _ that can participate in resonance in the

ortho position

resonance

Substituents on benzoic acid that can participate in _ in the

ortho position

ortho

Substituents on benzoic acid that can participate in resonance in the

_ position

intramolecular H bonding

_+ steric effect > resonance effect

steric

intramolecular H bonding + _ effect > resonance effect

resonance

intramolecular H bonding + steric effect > _ effect

Phenol

PI ELECTRON DELOCALIZATION/

RESONANCE ex

Ortho and Para

_ 2positions – resonance effect → stabilizes phenoxide ion

and increases acidity

Nitro group on phenol

resonance

Ortho and Para positions – _ effect → stabilizes phenoxide ion

and increases acidity

Nitro group on phenol

phenoxide ion

Ortho and Para positions – resonance effect → stabilizes _ and increases acidity

Nitro group on phenol

acidity

Ortho and Para positions – resonance effect → stabilizes phenoxide ion

and increases _

Nitro group on phenol