They are short-lived, high energy and highly reactive molecules. • They may be cations, anions or neutral species with one or more unpaired electrons.

Homolytic fission and heterolytic fission.

-E effect, the Electromeric shift of pi- electrons of a multiple bond is away from that atom to which the reagent gets attached.

• Carbon bearing a positive charge is called carbocation. • Carbocation has only six valence electrons. • Electron deficient species.

Acidity of carboxylic acid is decreased by the presence of bulky groups as they cause steric hindrance to the solvation of carboxylate ion through solvation.

Anti- staggered conformation of butane is more stable since the two methyl groups are far away from each other. In fully eclipsed conformation, the two methyl groups are near to each other. Hence it is least stable.

Because in chloroacetic acid -I effect of Cl group decreases electron density around carboxyl hydrogen. Also because of the dispersal of negative charge on the carboxylate ion, the ion is stabilized than acid. In acetic acid due to the +I effect of CH3 group acidity decreases.

This is because the two methyl groups sterically hinder the approach of alcohol.

in explanation

In But-1-ene, there are two hydrogen atoms attached to alpha carbon atom. Hence, two hyperconjugative interactions are possible. In But-2-ene, there are 6 hydrogens attached to alpha carbon atom and 6 hyperconjugative interactions are possible. As the number of hyperconjugative structures are greater for But-2-ene, it is more stable

They are neutral species with unpaired electrons. Highly reactive and is formed by homolytic fission.

The polarity induced in a molecule by the interaction of two pi- bonds or between a pi- bond and lone pair of electrons present

When a covalent bond breaks in an unsymmetrical manner such that one of the fragments retains both the bonding electrons, the process is called heterolytic bond fission or heterolysis.

The decrease in rate of esterification is due to steric effect on acids which hinders the approach of alcohol to reaction site on acids.

The pi electrons of benzene ring are uniformly delocalized. They are easily attacked by electrophiles. However, substituted benzene show +M or -M effect. The substituents can either donate or withdraw electron density from ring.

Electrophiles- They are electron deficient and can accept an electron pair in a reaction. They are lewis acids which are positively charged or neutral species.

(CH₃)₃C > (CH₃)₂CH > CH₃CH₂ > CH₃

In propene,CH3 group is attached to C=C that has a pi- bond. The sigma orbital of C-H bonds of CH3 is in conjugation with pi orbital of double bond

F-CH₂COOH >Cl- CH₂COOH > Br- CH₂COOH > I-CH₂COOH This is because the electronegativity order of halogens are F > Cl > Br > I

Since there are three Cl groups in trichloroacetic acid, -I effect would be more than in dichloroacetic acid. So acid strength of trichloroacetic acid is greater.

Acetaldehyde and CN-

Hyperconjugation is also called no-bond resonance since there is no real bond between Carbon and Hydrogen in hyperconjugative structures. But the H+ ion is bound firmly to pi bond and is not free to move.

NO2 is a group which shows – M effect. They make the benzene ring less reactive towards electrophilic substitution reactions by withdrawing electrons from the ring by resonance. Such groups are called deactivating groups or substituents.

1. Inductive effect 2. Electromeric effect 3. Mesomeric effect 4. Hyperconjugation 5. Steric effect

+E effect, the Electromeric shift of pi- electrons of a multiple bond is towards that atom to which reagent gets attached.

NH2 is a group which shows +M effect. They make the benzene ring more reactive towards electrophilic substitution reactions by donating electrons to the ring by resonance. Such groups are called activating groups or substituents.

+I EFFECT- The polarization of sigma bond due to the presence of electron donating groups.

Carbon atom have a tendency to form bonds between its own atoms to form long chains. This property is called catenation.

Formed by heterolytic cleavage of covalent bonds.

• effect of displacement of bonding electrons. • Electron displacement effect may be permanent or temporary.

Hyperconjugation

Curved arrow indicates the movement of electrons, not the movement of atoms.

pic

In cis-2-butene, the two bulky methyl groups are on the same side of double bond. They are close to each other and cause spatial crowding. In trans-2-butene,the two groups are on the opposite side of double bond and there is no crowding. So, cis-2-butene is less stable.

explaination

in explanation

I EFFECT- The polarization of sigma bond due to the presence of electron withdrawing groups.

The acid dissociation constant (Ka) of a solution is pKa. The pKa value is one method of determining an acid's strength. A lower pKa value denotes a more powerful acid. For example, a lower number indicates that the acid dissociates more entirely in water. As acid value increases Pka value decreases

Electrophiles, Nucleophiles and free radicals

Chloroacetic acid is stronger than acetic acid

• The polarization of a sigma bond due to electron withdrawing or electron donating effect of adjacent groups or atoms is called inductive effect or l effect. • It is a permanent electron displacement effect.

Organic chemistry is the chemistry of carbon compounds.

The intermediate species formed during the stepwise progress of a reaction to reach its preferred products are called reaction intermediates.

In terms of Inductive effect, we would expect trimethylamine is more basic than dimethylamine or methylamine because an increase in number of methyl groups increase the electron availability at Nitrogen atom. However, the order of basicity of the above amines in aqueous solution is as follows The lower basicity of trimethylamine is due to steric effect of the three methyl groups which hinders the approach of the proton and also hinders the stabilization of resulting trimethylammonium ion through solvation.

Cl. , CH₃. , C₆H₅

H+, Cl+, Br+,NO₂+,BF₃,AlCl₃ etc

Comparison of electron density of benzene, nitrobenzene and aniline

 Cabon atom in a cabocation is sp² hybridized.  The three sp² hybrid orbitals form σ-bonds with three groups or atoms.  One vacant p-orbital remain unhybridised and lies perpendicular to the plane.  Carbocation has trigonal planar shape with bond angle 120°.

Full arrowhead indicates the movement of two electrons simultaneously and half -headed arrow represent the movement of single electron

Temporary effect involving the complete transfer of a shared pair of pi- electrons of a multiple bond to one of the bonded atoms, in the presence of an attacking reagent

This is because the intensity of inductive effect decreases with increasing distance of electron withdrawing substituents.

GroupsWhen present adjacent to conjugated multiple bonds ,bring resonance by withdrawing pi-electrons of multiple bond thereby causing electron displacement towards themselves . The effect produced is called -R/-M effect. eg crotonaldehyde vinyl cyanide

H-COOH > CH₃-COOH > CH₃-CH₂-COOH Propanoic acid is least acidic due to the +I effect of CH2-CH3 group. Acetic acid is comparatively stronger and the strongest acid is formic acid

Electromeric effect

C=O, NO2, COOH

NO2 > CN > COOH > F > Cl > Br > I > OCH3

in explanation

carbocations, carbanions, free radicals etc

They are electron rich having lone pair of electrons. They are lewis bases which may be negatively charged ions or neutral molecules having lone pairs.

They affect the stability of the molecule as the groups do not get enough space for their accommodation and also there occurs repulsion between them. • They also obstruct the approach of attacking reagents.

OH- , H₂N- ,R-, NH₃, H₂O