Organic Chemistry for Physics: Lectures 1–4

Comprehensive practice flashcards defining core terms, metrics, principles, and nomenclature rules from Lectures 1 through 4 of Organic Chemistry for Physics.

Vis Vitalis (Life Force)

The historical doctrine proposing that organic matter can only be generated in-vivo (within living organisms) through an inherent vital force.

Wöhler Synthesis (1828)

The laboratory conversion of the inorganic salt ammonium cyanate into organic urea via heating, which historically disproved the vital force theory.

Organic Compound

A chemical substance composed of molecules containing carbon, with historical exceptions such as carbon oxides ($CO$, $CO_2$, $C_3O_2$), carbonic acid ($H_2CO_3$), bicarbonates, carbonates, and carbides ($CaC_2$, $Al_4C_3$).

Carbon-Carbon Bond Lengths and Energies

The structural and energetic metrics of carbon bonds: a $C-C$ single bond has a length of $154\,pm$ and an energy of $88\,kcal/mol$ ($368\,kJ/mol$); a $C=C$ double bond has a length of $142\,pm$ and an energy of $152\,kcal/mol$ ($636\,kJ/mol$); a $C\equiv C$ triple bond has a length of $126\,pm$ and an energy of $200\,kcal/mol$ ($837\,kJ/mol$).

Chemical Bond Types by Electronegativity Difference

Bond classifications based on $\Delta EN$: nonpolar covalent ($\Delta EN < 0.5$), polar covalent ($\Delta EN = 0.5\text{ to }1.7$), and ionic ($\Delta EN > 1.7$).

Line-Angle Formula (Skeletal Structure)

A molecular representation where bonds are represented as lines, carbon atoms are implicitly located at vertices and line terminals with sufficient implicit hydrogens to complete an octet, and heteroatoms with their attached hydrogens are explicitly drawn.

Functional Group

A specific structural arrangement of atoms that displays characteristic and predictable chemical reactivity regardless of the molecule in which it occurs.

Resonance Hybrid

The actual physical structure of a delocalized molecule, represented as a weighted average of two or more contributing canonical Lewis structures.

Canonical Structures (Resonance Forms)

Imaginary Lewis structures that differ solely in the spatial placement of $\pi$-electrons or non-bonding lone pairs, maintaining an identical $\sigma$-framework and atomic connectivity.

Curved Arrow Notation

A standardized visual notation that tracks the flow of electron pairs (using double-headed arrows) or single electrons (using fishhook arrows) from an electron source to an electron sink during reactions or resonance redistribution.

Electron Source

A region of high electron density that provides electrons in a chemical mechanism or resonance transfer, including $\pi$-electrons, non-bonded lone pairs, or single unshared electrons.

Electron Sink

An electron-deficient region that accepts electrons in a chemical mechanism or resonance transfer, such as an electronegative atom, an atom with an open shell, a positively charged atom, or an atom with an unshared single electron.

Coordinate Bond (Dative Bond)

A covalent two-electron bond formed when both bonding electrons originate entirely from a single atom's lone pair, such as the bond formed between the nitrogen of ammonia and the boron of boron trifluoride.

Major Resonance Contributor

The lowest-energy, most stable canonical contributor to a resonance hybrid, prioritized by: (1) filled octets on second-row atoms, (2) maximum bonds and minimum formal charge, (3) negative formal charge located on the most electronegative atom, and (4) minimized charge separation.

Inductive Effect

The shifting of electron density along a $\sigma$-bond framework caused by the electronegativity differences of adjacent atoms or functional groups.

Lewis Acid and Lewis Base

A Lewis acid is an electron-pair acceptor (electrophile) possessing an empty or easily vacated orbital; a Lewis base is an electron-pair donor (nucleophile) possessing non-bonding lone pairs.

$$pK_a$$

The negative base-10 logarithm of the acid dissociation constant ($-\log_{10}(K_a)$), where smaller or more negative values indicate stronger acids that possess more stable, weaker conjugate bases.

Alkane

A fully saturated aliphatic hydrocarbon containing only single $\sigma$-bonds between $sp^3$-hybridized carbon atoms with tetrahedral bond angles of $109.5^\circ$ and the general formula $C_n H_{2n+2}$.

Constitutional Isomers

Molecules that share the identical molecular formula but possess different connectivity patterns among their constituent atoms.

n-Undecane

A straight-chain eleven-carbon alkane with the molecular formula $C_{11}H_{24}$ that functions biologically as a cockroach aggregation pheromone.

Primary ($1^\circ$), Secondary ($2^\circ$), Tertiary ($3^\circ$), and Quaternary ($4^\circ$) Carbon

Classification of an $sp^3$ carbon based directly on the number of other carbon atoms covalently bound to it: one ($1^\circ$), two ($2^\circ$), three ($3^\circ$), or four ($4^\circ$).

Iso- Subunit Prefix

A non-systematic structural prefix denoting an alkyl group with two methyl groups attached to the terminal carbon of the substituent chain.

Sec- Subunit Prefix

A non-systematic structural prefix indicating that the carbon atom attached to the main parent molecular chain is itself bonded to two other carbon atoms.

Tert- Subunit Prefix

A non-systematic structural prefix indicating that the carbon atom attached to the main parent molecular chain is itself bonded to three other carbon atoms.

Neo- Subunit Prefix

A non-systematic structural prefix designating a branched alkyl group bearing three methyl groups located at the terminal carbon atom of the branch.

Conformational Analysis

The quantitative thermodynamic and structural investigation of the energy changes and spatial orientations resulting from single-bond rotations within a molecule.

Torsional Strain

The increase in potential energy caused by electron-electron repulsion between aligned bonding electron pairs on adjacent atoms when a bond rotates into an eclipsed conformation.

Steric Strain

The repulsive destabilization that occurs when non-bonded atoms or groups are forced closer together than their respective van der Waals radii permit.

Gauche Conformation

A specific staggered spatial arrangement where two vicinal substituents share a dihedral (torsion) angle of approximately $60^\circ$.

Anti Conformation

A specific staggered spatial arrangement where two vicinal substituents share a maximum dihedral (torsion) angle of $180^\circ$, minimizing steric interactions.

Ethane Rotational Barrier

The energy requirement of $2.9\,kcal/mol$ ($12.3\,kJ/mol$) needed to rotate from the lowest-energy staggered conformation to the highest-energy eclipsed conformation.

Hyperconjugation in Staggered Ethane

The stabilizing electronic overlap occurring between filled $\sigma_{CH}$ bonding orbitals and adjacent empty $\sigma^*_{CH}$ antibonding orbitals, lowering the energy of the staggered conformation relative to the eclipsed form.

Cycloalkane

A cyclic saturated hydrocarbon composed of rings of $sp^3$-hybridized carbon atoms governed by the general molecular formula $C_n H_{2n}$.

Ring Strain

The total thermodynamic destabilization of a cyclic molecule consisting of angle strain (deviation from the ideal $109.5^\circ$ tetrahedral angle), torsional strain (eclipsing of ring bonds), and transannular steric strain.

Chair Conformation

The all-staggered, strain-free three-dimensional conformation adopted by cyclohexane rings possessing tetrahedral carbon bond angles and zero angle or torsional strain.

Axial Bonds

The six cyclohexane chair C-H or substituent bonds oriented perpendicular to the approximate average plane of the ring, directed vertically alternating straight up and straight down.

Equatorial Bonds

The six cyclohexane chair C-H or substituent bonds extending radially outward around the ring equator, oriented slightly up or down parallel to alternating ring bonds.

Ring Inversion (Chair Flip)

The conformational interconversion of cyclohexane through half-chair, twist-boat, and boat conformations that converts all axial substituents into equatorial substituents and vice versa, overcoming an energetic barrier of approximately $10.3\,kcal/mol$.

1,3-Diaxial Interaction

The steric strain resulting from repulsive gauche-type non-bonded interactions between an axial substituent on a cyclohexane chair and the axial hydrogens or groups located two carbons away at positions 3 and 5.

A-Value

A thermodynamic parameter quantifying the conformational free energy preference of a substituent on a cyclohexane ring to occupy an equatorial position over an axial position.

Conformational Lock (tert-Butyl Group)

The complete bias exerted by a bulky tert-butyl substituent on a cyclohexane ring that forces the ring into a chair conformation where the tert-butyl group is exclusively equatorial due to severe 1,3-diaxial strain in the axial position.

Decalin Isomer Conformational Inversion

The stereochemical distinction in fused bicyclo[4.4.0]decanes wherein cis-decalin can undergo chair-chair ring inversion, whereas trans-decalin is conformationally rigid and locked against ring flipping.