Electronegativity in Organic Chemistry

Definition by Linus Pauling

• Electronegativity refers to the power of an atom in a molecule to attract electrons to itself.
• Important for comparing atoms within a molecule.

Pauling Scale

• Linus Pauling calculated electronegativity values for elements.
• Useful to compare elements' electronegativities using the periodic table designed for organic chemistry.

Electronegativity Examples

Carbon vs. Oxygen

• Carbon: Electronegativity = 2.5
• Oxygen: Electronegativity = 3.5
• Oxygen is more electronegative than carbon.
• Electrons in covalent bonds shared unequally, with oxygen pulling electrons closer.
• Oxygen gets a partial negative charge, carbon a partial positive charge.
• Results in a polar covalent bond.

Carbon vs. Carbon

• Both carbons have an electronegativity of 2.5.
• No difference in electronegativity; electrons shared equally.
• Non-polar covalent bond.

Carbon vs. Hydrogen

• Carbon: Electronegativity = 2.5
• Hydrogen: Electronegativity = 2.1
• Difference is 0.4, considered a non-polar covalent bond.

Electronegativity Differences and Bond Types

• 0.4 or less: Non-polar covalent bond
• Greater than 0.5: Polar covalent bond
• Around 1.7: Ionic bond

More Examples

Oxygen vs. Hydrogen

• Oxygen: Electronegativity = 3.5
• Hydrogen: Electronegativity = 2.1
• Difference of 1.4, polar covalent bond.

Carbon vs. Lithium

• Carbon: Electronegativity = 2.5
• Lithium: Electronegativity = 1
• Difference of 1.5, can be considered polar covalent or ionic depending on context.

Sodium Chloride

• Sodium: Electronegativity = 0.9
• Chlorine: Electronegativity = 3
• Difference of 2.1, creating an ionic bond where chlorine steals electrons.

Summary

• Electronegativity is crucial for understanding organic chemistry mechanisms.
• Relative differences are more important in practice than exact numbers.
• Understanding basic differences like "oxygen is more electronegative than carbon" is foundational.