Haloalkanes and Haloarenes

Chiral Molecule

Molecule without POS and COS. These are always optically active.

Centre Of Symmetry

An imaginary point in a molecule such that moving 180 degree in any direction to an equal distance leads to an identical atom or group

Chiral centre

Any sp3 hybridised centre through which 4 different groups are attached

Do we check COS in 2d?

No

Compounds containing one chiral centre are always optically active. [T/F]

T

Compounds containing more than one chiral centre are always optically active. [T/F]

F. May or may not be active

Compounds containing no chiral centre are never optically active [T/F]

F. May or may not be active

Enantiomers

Enantiomers are non-superimposable mirror images of each other and example of optical isomers. Have same chemical and physical properties except rotation towards PPL

Diastereomers

Stereoisomers that are not mirror images of each other

All enantiomers are optical isomers, but not all optical isomers are enantiomers. [T/F]

T, diastereomers (non-mirror-image stereoisomers) can also be optically active if they lack symmetry elements.

Meso compounds

A compound which contains more than one chiral centre and is optically inactive(POS). Meso compound is optically inactive due to internal compensation.

racemic mixture

A mixture that contains equal amounts of the (+) and (-) enantiomers. Racemic mixtures are not optically active.

Resolution

The process of separation of racemic mixture into enantiomeric form.

Racemisation

The process of conversion of optically active compound into a racemic mixture. Converting half of the compound into other form.

Example of OA when no chiral centre in a molecule?

Allene and Biphenyl

Odd no. of pie bond containing allenes are always optically inactive. [T/F]

T

Allenes are also known as

Commulated alkene

Minimum condition to show OA when no chiral centre?

Nucelophiles

These donate: neutral lone pair e- density, negatively charged lone pair e- density, pie bond e- density

All bases are nucleophiles but not all nucleophiles are bases. [T/F]

False, All nucleophiles are bases but not all bases are nucleophiles.

Write order of nucleophilicity:
1) NH2-,CH3-,OH-,F-
2) F-,Br-,Cl-,I-
3) Ch3COO-,phO-,OH-,RO-

1) CH3- > NH2- > OH- > F-
2) F- > Cl- > Br- > I-
3) RO- > OH- > phO- > CH3COO-

Stronger the base better is the leaving group. [T/F]

F, weaker the base better is the leaving group

Order of LG in halogens?

F- < Cl- <Br- < I-

Which is stronger Nu?

Examples of PPS

H2O, ROH, RCOOH etc

Examples of PAS

Acetone, DMSO, DMF, THF etc

Order of Nu of halogens in PPS vs PAS

PPS: F- > Cl- > Br- > I-
PAS: F- < Cl- <Br- < I-

Write mechanism of SN1

Mentos for SN1 (9)

Write SN2 mechanism and mentos (8)

Elimination Reaction

Favourable at high temp

Generally thermodynamically stable pdt. is formed as major

Alpha elimination and beta elimination

Define Alpha and beta elimination

Alpha: Both H and LG eliminate from same carbon
Beta: H and LG generally eliminate from adjacent carbon

Write E1 mechanism and mentos (4)

Write E2 mechanism and mentos (4)

Write E1CB mechanism and mentos (4)

Preparation Of Haloalkane
1) From Alcohol
2) PX3 & PX5
3) Darzens Method
4) From Alkane
5) From Alkene

.

Halogen Exchange methods? (Finkelstein and Swartz)

Preparation of Aryl Halide
1)ESR
2) From Diazonium salt ( 4)

NSR in alkyl halide
Aq KOH, CaCO3,Moist Ag2O. RONa. KCN, AgCN, KNO2, AgNO2, NH3.
Examples of ambidentate nucleophiles

→ Reduction with alkyl halide
→ Rxn with Metal
→ ESR in Aryl halide (Hint: Sulphonation, nitration etc)

Why does NSR in aryl halide does not undergo easily (4)

Dows Process under drastic conditions and when we add EWG (NO2)

→ Franklund Reaction
→ Corey-House synthesis
→ SNar mechanism and rate

Benzyne Mechanism

→ Reaction with Chloral/ DDT method of preparation
→ Carbylamine test

Haloform Reaction

Polyhalogen Compounds
I) Geminal and Vicinal Halides (Preparation and properties)

DDT Properties
CCl4 Prep and Prop
CHI3 Properties

CH2CL2 Properties
Freons properties
Chloroform Prep and Prop