Interdisciplinarity: Chemistry ↔ BiologyDr. Fida Mohammad, GIKI- Topi

Learning from: ►How chemists think ►What they do & How they do it

Attitude until 1828 Organic compounds made

by plants or animals cannot be

made by man

Birth of Molecules

Dalton’s theory 1808

►Two or more than two atoms sticking together form molecules & that during chemical reactions atoms remain intact

OH + HCl → H2O + Cl

☺Maxwell: Nature, Sept 1873,

13 page article ” Molecule ”

Birth of Organic Chemistry:Woehler synthesis- 1828

►He produced urea outside kidney

►He discovered Isomerism-I HCN vs HNC

Isomerism ( connectivity )

Van’t Hoff considers third dimensionremoving isomer paradox (1874 )

Two Isomers

No Isomer

Cl

Cl

Van’t Hoff & Le Bel: Tetrahedral carbon atom also explains optical activity

Chirality enters chemistry

Carbon atom insists on 109º angle

Chair or Boat form ?Can moleculesbend, twistcurl, foldcoil, turn

Puckered ringsConformations

Molecular angle is adjustedto relieve strain

ZigzagMolecules

Precise measurements of angles and bond lengths

What if the angle in water changes to 109º ?

Distribution of atoms in molecules - I

Distribution of charge in molecules - II:

Dipole forces

Dispersion forces

►Be careful with charge distribution in CO►Don’t underestimate dispersion forces

Dispersion forces depend on shape also

CH3-CH2-CH2-CH2-CH3

CH3-CH2-CH2-CH2-CH3

CH3-C-CH3

CH3

CH3

CH3-C-CH3

CH3

CH3

Kevlar ( Hydrogen bonding )

Fiber Axis

Twisting, folding,coiling molecule

Great debate on Macromolecules: formation, size, flexibility, molar mass

:

:

Ultra-high-molecular-weight-polyethylene ( UHMWPE )Bullet proof Jackets

Dispersion forces

Alternative structure for macromolecules

The restless MoleculesTranslationRotationVibration

Distance between base pairs = 340pm

Rotation from base to base = 36º

No. of bases per turn = 10

Length of DNA from one chromosome = 5 cm

Molar mass= 1000 tons

Unraveling the code of life

Understanding genetic make-up and

Health Forecasting

Definition of chemistry: transformation of matter but how ?

.

Cyclobutane Ethylene

Femto-second chemistry( Intermediates, transition states etc )

Exothermic reaction: where does the energy go ?

F + D2 → DF ( v ) + H + ∆H (147 kJ/mol )

V Rel. Amount

0 01 22 443 1004 49

Studied for star war