University:
York University
Course:
CHEM 1000 | Chemical Structure
Academic year:

2021
Views:

287

Pages:

2
Author:

Niklas

Bond Strength Trends: 1. X≡Y > X=Y > X-Y Triple Bonds are stronger than double bonds, which are stronger than single bonds. 2. Polarity C-F > C-O > C-N > C-C > C-H ↑ ↑ polarity 3. Periodicity C-F >> C-Cl > C-Br > C-I ↑ MORE IA=↑ Stronger Bond ↑ High Polarity ↑ Atoms of similar radii 4. O-H > S-H ↑ Polar ↑ Stronger ↑ Smaller overlap of orbitals 5. C≡C >> C=C >> C-C ↑ ↑ ↑ ↑ Very strong ↑ Two I elements ↑ Poor overlap * Dipole Moments: arise when atoms have differing electronegativities - one atom is δ+ - one atom is δ- → leads to a DIPOLE X-Y ↑ y is MORE I than x * Bond has Dipole Moment(µ) * µ is a measure of Bond Polarity. * µ = Q x R * µ is given a unit - Debye (D) = Charge/distance Why are DMs important? Physical Properties: A: δ+ δ- A--B B: δ+ δ- A---B Attraction → affects bp, mp, etc. Reactivity: δ+ δ- A---B More likely to accept e- Two Types of Dipoles: Bond Dipoles: single atoms in a covalent bond Molecular Dipoles: vector sum of all Bond Dipoles Physically measured Property intrinsic to a given molecule Examples: Methane H | H-C-H | H (µ = 0) - nonpolar CHCl₃ Cl | H-C-Cl | Cl (µ = 1.9 D) CCl₄ Cl | Cl-C-Cl | Cl (µ = 0) H₂O H | O / \ H H (µ = 1.84 D)