Organic Chemistry Chapter 2: Acids and Bases; Functional Groups

Vocabulary flashcards covering polarity, physical property trends, acid-base theories, pKa/pKb, electrophiles/nucleophiles, and classes of organic functional groups from Chapter 2.

Debye (D)

The unit of measurement for dipole moments, where $10^{-30} \times 3.34$ coulomb-meters equals one Debye ($1\,D = 3.34 \times 10^{-30}\,C\,m$).

Dipole Moment Formula

The equation used to calculate dipole moment in debyes, expressed as $\,\mu(\text{in debyes}) = 4.8 \times \delta(\text{electron charge}) \times d(\text{in angstroms})$.

Molecular Dipole Moment

The vector sum of individual bond dipole moments in a molecule, which depends on both the magnitudes and directions of the bond dipoles.

London Dispersion Forces

Weak Van der Waals attractive forces arising from transient dipole moments that induce correlated temporary dipoles in nearby molecules.

Effect of Branching on Boiling Point

Increased chain branching makes molecules more spherical, reducing their surface area and weakening attractive London dispersion forces, which drops the boiling point.

Hydrogen Bonding

A strong dipole-dipole attraction (approximately $20\,kJ/mol$) occurring when a polarized hydrogen on an O-H or N-H group is attracted to a lone pair on oxygen or nitrogen.

Arrhenius Acid

A substance that dissociates in water to produce hydronium ions ($H_3O^+$), also referred to as oxonium ions.

Arrhenius Base

A substance that dissociates in water to produce hydroxide ions ($OH^-$).

Brønsted-Lowry Acid

A chemical species capable of donating a proton ($H^+$).

Brønsted-Lowry Base

A chemical species capable of accepting a proton ($H^+$).

Conjugate Acid

The species formed when a base accepts a proton, which is then capable of donating that proton in the reverse reaction.

Conjugate Base

The species remaining after an acid donates its proton, which is then capable of accepting a proton back in the reverse reaction.

pK_a

The negative logarithm of the acid dissociation constant, defined as $pK_a = -\log_{10}(K_a)$, where smaller values correspond to stronger acids.

Water Conjugate Pair Relationship

The quantitative relationship between acid and base constants for conjugate pairs in water, given by $pK_a + pK_b = 14$.

Acid-Base Equilibrium Principle

An acid-base equilibrium always favors the formation of the weaker acid and weaker base, corresponding to the species with larger $pK_a$ and $pK_b$ values.

Amphoteric

The property of a substance, such as water, that allows it to act as either an acid or a base.

Levelling Effect

The phenomenon where the strength of strong acids or bases in a solvent is limited to the strength of the solvent's conjugate acid (such as $H_3O^+$) or conjugate base (such as $OH^-$).

Electronegativity Effect on Acidity

Higher electronegativity of the atom bonded to hydrogen increases acid strength by better accommodating negative charge on the conjugate base.

Anion Size Effect on Acidity

Larger conjugate base anions delocalize negative charge over a greater volume, making size a more dominant factor than electronegativity for increasing acidity down a column in the periodic table.

Inductive Effect on Acidity

The stabilization of a conjugate base through sigma bonds by nearby electron-withdrawing atoms or groups, which enhances acidity as proximity and number of groups increase.

Hybridization Effect on Acidity

Orbitals with greater s-character ($sp > sp^2 > sp^3$) hold unshared electrons closer to the nucleus, making the conjugate base more stable and the parent compound more acidic.

Resonance Effect on Acidity

Delocalization of negative charge across multiple atoms in the conjugate base stabilizes the anion, significantly increasing the acidity of the parent compound.

Nucleophile (Lewis Base)

An electron-rich species that donates an electron pair to an electron-deficient atom to form a chemical bond.

Electrophile (Lewis Acid)

An electron-poor species that accepts an electron pair from an electron-rich species to form a chemical bond.

Curved-Arrow Formalism

A notation system showing the movement of an electron pair from the electron donor (nucleophile/base) to the electron acceptor (electrophile/acid).

Types of Reaction Arrows

Standard symbols representing specific processes: reaction direction (straight arrow), equilibrium (double harpoon), resonance (double-headed straight arrow), Lewis acid-base electron flow (red curved arrow), and imaginary resonance electron movement (green curved arrow).

Hydrocarbons

Organic compounds composed entirely of carbon and hydrogen atoms.

Alkanes

Saturated hydrocarbons containing only single bonds between carbon atoms ($sp^3$ hybridized) with the general molecular formula $C_n H_{2n+2}$.

Cycloalkanes

Saturated hydrocarbons in which sp3 carbons form a closed ring, with the general formula $C_n H_{2n}$.

Alkenes

Unsaturated hydrocarbons containing at least one carbon-carbon double bond ($sp^2$ hybridized carbons).

Alkynes

Unsaturated hydrocarbons containing at least one carbon-carbon triple bond ($sp$ hybridized carbons).

Aromatic Hydrocarbons

Unsaturated cyclic hydrocarbons containing a benzene ring or related resonant ring system.

Alcohols

Organic compounds containing a hydroxyl group ($-OH$) as their primary functional group, designated by the suffix '-ol'.

Ethers

Organic compounds containing an oxygen atom bonded to two alkyl or aryl groups ($R-O-R'$).

Aldehydes

Organic compounds featuring a carbonyl group ($C=O$) bonded to at least one hydrogen atom ($R-CHO$), designated by the suffix '-al'.

Ketones

Organic compounds featuring a carbonyl group ($C=O$) bonded to two alkyl or aryl groups ($R-CO-R'$), designated by the suffix '-one'.

Carboxylic Acids

Organic compounds containing a carboxyl group ($-COOH$), consisting of a carbonyl group directly attached to a hydroxyl group.

Amines

Organic derivatives of ammonia ($R_3N$) where one or more hydrogens are substituted by alkyl or aryl groups, acting as moderately strong bases.

Amides

Carboxylic acid derivatives containing a nitrogen atom bonded directly to a carbonyl carbon ($R-CO-NR'_2$), functioning as very weak bases due to resonance delocalization.

Nitriles

Organic compounds containing a terminal cyano functional group ($-C \equiv N$).