Organic Chemistry Notes — (quiz 2)Acid/Base Equilibria, Orbitals, Lewis Acids/Bases, and Nomenclature

A comprehensive set of vocabulary-style flashcards drawn from lecture notes, covering acid/base equilibria, orbital theory, Lewis acid–base chemistry, and hydrocarbon nomenclature.

Equilibrium favors the weaker acid/base pair

In acid-base equilibria, the reaction shifts toward the side containing the weaker acid and weaker base (the conjugate pair with the higher pKa).

pKa

The negative logarithm of Ka; a numeric measure of acid strength; lower pKa = stronger acid, higher pKa = weaker acid.

Ka

Acid dissociation constant; the equilibrium constant for an acid donating a proton in water.

Conjugate base

The species formed when an acid donates a proton.

Conjugate acid

The species formed when a base accepts a proton.

Resonance stabilization

Delocalization of electrons across multiple atoms, stabilizing a charged species and lowering energy.

Inductive effect

Electron-withdrawing or donating effect transmitted through sigma bonds due to electronegativity differences.

Electronegativity

Tendency of an atom to attract electrons in a bond; influences acidity and base strength.

Acidity trend with electronegativity

More electronegative atoms attached to the acidic hydrogen generally increase acidity by stabilizing the conjugate base.

Size effect on acidity

Atomic size can influence the stability of the conjugate base; in some cases smaller, highly electronegative atoms can stabilize charge better, affecting acidity.

Orbital type and acidity

Which orbital hosts the negative charge in the conjugate base (e.g., sp, sp2, sp3) affects stability and hence acidity.

sp hybridization

Hybridization with 50% s-character; linear geometry; often stabilizes negative charge more than sp2 or sp3.

sp2 hybridization

Hybridization with about 33% s-character; trigonal planar geometry.

sp3 hybridization

Hybridization with about 25% s-character; tetrahedral geometry.

s-character and conjugate base stability

Higher s-character in the orbital bearing the negative charge stabilizes the conjugate base, increasing acidity.

Localization vs Delocalization (resonance)

Localization confines charge to one atom; delocalization distributes charge over a conjugated system, stabilizing it.

Terminal alkyne acidity concept

Conjugate base stability in alkynes is enhanced by the involvement of an sp-hybridized orbital, contributing to observable acidity.

Bronsted–Lowry acid

A substance that donates a proton (H+).

Bronsted–Lowry base

A substance that accepts a proton (H+).

Lewis acid

A substance that accepts an electron pair.

Lewis base

A substance that donates an electron pair.

Electrophile

An electron-poor species that accepts electrons in a reaction.

Nucleophile

An electron-rich species that donates electrons to an electrophile.

Lewis acid-base adduct

A complex formed when a Lewis base donates an electron pair to a Lewis acid.

Alkane

A saturated hydrocarbon with only single C–C bonds; general formula CnH2n+2; tetrahedral carbons.

Acyclic

Open-chain hydrocarbon not part of a ring.

Cycloalkane

A saturated cyclic hydrocarbon (e.g., cyclopropane, cyclohexane).

Longest chain rule

In hydrocarbon naming, identify the longest continuous carbon chain to determine the parent name.

Parent names (first 10 carbon)

meth-, eth-, prop-, but-, pent-, hex-, hept-, oct-, non-, dec- are the common prefixes for the number of carbons in the parent chain.

Substituent

An atom or group attached to the parent chain that takes the place of a hydrogen.

Methyl group

CH3 substituent on a carbon skeleton.

Ethyl group

CH2CH3 substituent on a carbon skeleton.

Propyl group

C3 substituent; includes n-propyl and branched forms (isopropyl).

Isopropyl

Common name for the substituent 1-methyl ethyl; IUPAC name is propan-2-yl.

Primary/Secondary/Tertiary carbon

Classification based on how many carbon atoms are directly bonded to the carbon: primary (1), secondary (2), tertiary (3).

Cycloalkane naming

Names begin with cyclo- followed by the ring size (cyclopropane, cyclohexane) and substituents as needed.

IUPAC vs common names

IUPAC provides systematic names; common/trade names are often used for simple substituents (e.g., isopropyl).

Locants

Numbers assigned to substituents on the parent chain to indicate their positions; choose the lowest set of locants.

Branching

Arrangement of carbon substituents around the parent chain; affects hydrocarbon naming and properties.