General organic chemistry

How is electron density related to charge and size?

Electron density ↑ with higher charge, ↓ with larger size

What happens to reactants and reagents before forming products?

They go through a transition state or reactive intermediate.

What is electronegativity?

it’s the tendency of an atom to attract a shared electron pair in a covalent bond.

Arrange in descending order of electron density: A⁻, A, A⁺

A⁻ > A (neutral) > A

What are electronic displacement effects?

shifting of electrons in a molecule due to different influences.

How many types of electronic displacement effects are there?

Permanent effects and Temporary effects.

Which effects are permanent electronic effects?

Inductive effect, Mesomeric effect, Hyperconjugation.

Which effect is a temporary electronic effect?

Electromeric effect.

What is the inductive effect?

A permanent shift of electron density along a chain of sigma bonds due to difference in electronegativity between atoms or groups.

Through which bonds does inductive effect operate?

Sigma (σ) bonds only.

is inductive effect distance dependent?

Yes it is neglected after 3rd carbon

What is +I (positive inductive) effect?

When an electron-donating group is attached, pushing electron density toward the chain.

What charge develops on adjacent atoms in +I effect?

Adjacent atoms develop a partial negative charge (δ⁻).

Order of +I effect (strongest → weakest)?

-CH2

-NH

–O⁻

–COO⁻

–C(CH₃)₃

–CH(CH₃)₂

–CH₂CH₃

–CH₃

-T

–D

–H

What is −I (negative inductive) effect?

When an electron-withdrawing group pulls electron density away from the chain.

What charge develops on adjacent atoms in −I effect?

djacent atoms develop a partial positive charge (δ⁺).

Order of −I effect (strongest → weakest)?

NR₃⁺

SR₂

NH₃⁺

NO₂

SO₂R

CN

CHO

COOH

F

Cl

Br

I

OR

OH

Alkyne

NH₂

C₆H₅

Alkene

H

Which I group makes an anion more stable?

-I (ewg)

Relation of acidic strength with +I and -I

-I ∝Acidic strength ∝ 1/+I

Which I group makes carbocation more stable?

State the relation between the stability of carbocation wrt I groups

+I group

Stability of carbocation ∝+I ∝ 1/-I

Which I group makes carbanion more stable?

State the relation between the stability of carbanion wrt I groups

-I group

Stability of Carbanion∝-I∝1/+I

Definition of resonance

Delocalisation of π electrons in a conjugated system

What are resonating structures and what is a resonance hybrid

When a single Lewis structure can’t explain all the properties of a molecule, more than one Lewis structure is required.

These structures are called resonating structures.

Resonating structures are hypothetical

The resonance hybrid is the real structure.

Compare stability of neutral resonance structure and a charged resonance structure

Stability of neutral structure is higher than that of charged structures

Effect on stability by number of pi bonds

Stability increases with increase in pi bonds

Which is more stable: negative charge or positive charge?

Negative charge is more stable than positive charge

How does negative charge stability change across a period?

Left → Right : stability increases

How does negative charge stability change down a group?

Top → Bottom : stability increases

Relation of stability and charge separation of unlike charges on resonating structures.

Stability decreases with increase in charge separation.

Relation of stability and charge separation of like charges on resonating structures.

Stability increases with increase in charge separation.

What is a localized lone pair?

lone pair that doesn’t take part in resonance

What is a delocalized lone pair?

lone pair that takes part in resonance

Effect of conjugation on bond length

Bond length of 2 atoms partaking in a conjugated system is relatively smaller

Relation between stability and no. of benzene rings

Stability ∝ no. of benzene rings

2 separated benzenoid rings or 2 fused benzenoid rings, which is more stable?

2 separated benzenoid rings are more stable

What is mesomeric effect?

Donation or withdrawal of electron density to the conjugated system by a functional group.

+M effect

Donation of electron density to the conjugated system by a functional group.

-M effect

Withdrawal of electron density from the conjugated system by a functional group

How do you identify +M group