Advices For Studying Organic Chemistry

Hydrogen bonding (red dotted lines) in the α-helix structure of proteins.

2.15 SUMMARY OF ATTRACTIVE ELECTRIC FORCES

Table 2.6 Attractive Electric Forces

Electric Force Strength Relative Type Example

Cation-anion

(in a crystal) Very strong^ Lithium fluoride crystal lattice

Covalent bonds

Strong

(140-523 kJ

mol–1)

Shared electron pairs

H–H (435 kJ mol–1)

CH 3 –CH 3 (370 kJ mol–1)

I–I (150 kJ mol–1)

Ion-dipole Moderate

δ−

δ−

δ− δ−

δ+

δ+

δ+ δ+

Na＋ in water (see Fig. 2.9)

Dipole-dipole

(including

hydrogen

bonds)

Moderate to

weak (4-38 kJ

mol–1)^

δZ− Hδ+

O

δ−O

H

R

H R

δ+ δ− δ+

and

H 3 C Clδ− Clδ−

δ+

H 3 C

δ+

van der Waals Variable Transient dipole Interactions between methane molecules

2.16 INFRARED SPECTROSCOPY: AN INSTRUMENTAL METHOD