Dipole Moment Calculator

The electric dipole moment (μ) measures the separation of positive and negative charge in a molecule. It determines polarity, intermolecular forces, and many physical properties.

Formula:

μ = q × d

Where:

• μ = dipole moment (Debye or C·m)
• q = magnitude of partial charges (in units of electron charge e)
• d = distance between charge centers (pm or Å)

Unit conversion: 1 Debye (D) = 3.336 × 10⁻³⁰ C·m

For bond dipoles, a useful working formula: μ (Debye) = 4.803 × q_fraction × d (Å)

Where q_fraction is the fractional charge (0 to 1, from electronegativity difference).

Common molecular dipole moments:

Vector addition for molecular dipoles: If a molecule has multiple bond dipoles, the net molecular dipole is the vector sum. Symmetric molecules (linear, trigonal planar, tetrahedral with identical substituents) have μ = 0 even though each bond is polar.

μ_net = √(Σμᵢ²) for perpendicular bonds μ_net = |μ₁ + μ₂ + 2μ₁μ₂cos(θ)| for bonds at angle θ

Effects of dipole moment:

• Boiling point: Higher μ → stronger dipole-dipole forces → higher bp
• Solubility: “Like dissolves like” — polar solvents dissolve polar solutes
• Dielectric constant: High-μ solvents have large dielectric constants (water: 78.4)
• Microwave absorption: Polar molecules absorb microwave radiation (basis of microwave cooking)

Debye unit origin: Named after Peter Debye (1884–1966), Dutch-American physicist. 1 D is approximately the dipole moment of a pair of charges ±0.2e separated by 1 Å.