CHEM 0310 — Organic Chemistry 1

CHEM 0310 Study Guide

Organic Chemistry 1

Organic chemistry asks how molecular structure controls properties and reactions. Pitt's published Fall 2025 CHEM 0310 schedule includes bonding, acid–base chemistry, alkanes, cycloalkanes, stereochemistry, haloalkanes, alcohols, ethers, NMR, alkenes, and alkynes. Scope: Pitt CHEM 0310 syllabus.

These original notes and invented examples form a study framework. Use your instructor's reaction list for exact reagent coverage. Condensed structures such as CH_{3}CH_{2}OH are editable in a document, but practice drawing line structures, wedges, dashes, and electron-pushing arrows on paper as well.

How the material fits together

Structure before reactions

Count valence electrons, assign formal charges, and draw reasonable resonance contributors. Decide which atoms are electron-rich and electron-poor. Recognize sp^{3}, sp^{2}, and sp centers; connect those geometries to bond angles and restricted rotation. Compare constitutional isomers before considering stereoisomers.

Conformation and stereochemistry

Use Newman projections to compare conformations and chair drawings to analyze cyclohexanes. Bulky substituents often favor equatorial positions, but a chair flip does not change whether a substituent is up or down. For stereochemistry, identify stereogenic centers, assign priorities, orient the lowest-priority group, and then determine R or S. Check symmetry before counting stereoisomers.

Mechanisms and reactivity

An electron-pushing arrow starts at an electron pair or bond and ends where those electrons go. Check total charge after every step. Acid–base steps, substitution, elimination, and addition are recurring patterns. A reaction prediction should consider substrate structure, reagent behavior, solvent, temperature, and possible rearrangements together.

Structure identification

Combine molecular formula, unsaturation, NMR signal count, integration, splitting, and chemical shift. A single clue rarely identifies a molecule. Propose a structure, then check every observation against it.

Important vocabulary

Functional group: Structural feature associated with characteristic reactivity.
Sigma bond: Bond with electron density along the internuclear axis.
Pi bond: Bonding interaction from side-by-side orbital overlap.
Hybridization: Orbital-mixing model used to describe local bonding geometry.
Resonance contributor: One electron-bookkeeping representation of a delocalized structure.
Inductive effect: Influence transmitted through sigma bonds by electronegativity or charge.
Hyperconjugation: Stabilizing interaction involving a sigma bond and an adjacent suitable orbital.
Nucleophile: Electron-pair donor in a bond-forming reaction.
Electrophile: Electron-pair acceptor in a bond-forming reaction.
Leaving group: Group that departs with the bonding electron pair in a heterolytic step.
Carbocation: Carbon-centered cation with an electron-deficient carbon.
Transition state: High-energy configuration at a reaction barrier, not an isolable intermediate.
Intermediate: Species at a local energy minimum between reaction steps.
Constitutional isomers: Same molecular formula but different connectivity.
Conformers: Structures interconverted by rotations or other conformational changes without changing connectivity.
Enantiomers: Nonsuperimposable mirror-image stereoisomers.
Diastereomers: Stereoisomers that are not mirror images.
Meso compound: Achiral compound containing stereogenic elements because of its overall symmetry.
Racemic mixture: Equal amounts of a pair of enantiomers.
Stereospecific reaction: Different stereoisomeric reactants lead to specifically related stereoisomeric products.
Stereoselective reaction: Reaction favoring one stereoisomeric product over another.
Regioselectivity: Preference for reaction at one position or orientation.
Steric hindrance: Reduced accessibility caused by nearby atoms or groups.
Protic solvent: Solvent with an O–H or N–H group capable of relevant hydrogen-bond donation.
Chemical shift: NMR resonance position relative to a reference, usually in ppm.
Integration: NMR signal area used to infer relative numbers of nuclei under appropriate conditions.
Coupling: Interaction between nuclei that can split NMR signals.

Essential formulas and relationships

Formal charge = valence electrons − nonbonding electrons − bonding electrons/2. Check the sum against the species' total charge.
Degree of unsaturation DBE = (2C + 2 + N − H − X)/2, for ordinary closed-shell formulas containing C, H, N, O, S, and halogens X under standard valence assumptions. O and divalent S do not enter the count. A ring or double bond contributes 1; a triple bond contributes 2.
Ka ≈ [H_{3}O^{+}][A^{-}]/[HA] in the dilute-solution concentration convention; pKa = −log_{10}Ka.
For HA + B^{-} ⇌ A^{-} + HB, K ≈ 10^[pKa(HB) − pKa(HA)], using comparable pKa values in the same solvent and consistent standard states.
ΔG° = −RT ln K; ΔG° < 0 corresponds to K > 1 at the specified temperature.
Arrhenius form k = A exp[−Ea/(RT)] relates a rate constant to temperature in its applicable regime. R and Ea must use consistent energy units.
SN1 rate = k[substrate] for the simple unimolecular rate-limiting ionization model.
SN2 rate = k[substrate][nucleophile] for the standard bimolecular model.
E1 rate = k[substrate] and E2 rate = k[substrate][base] for the elementary models studied in introductory courses.
Maximum stereoisomer count = 2^{n} for n independent tetrahedral stereocenters before symmetry reductions and other constraints.
Enantiomeric excess ee = |%R − %S| for a mixture containing only that enantiomer pair.
Specific rotation [α] = αobserved/(ℓc) in one common convention, with ℓ in decimeters and c in g/mL. Some references use other concentration conventions; record wavelength, temperature, solvent, and units.
NMR chemical shift δ = (frequency difference/reference spectrometer frequency) × 10^{6}, with frequencies expressed in the same units.
n + 1 splitting rule: A proton set coupled to n equivalent spin-1/2 neighboring protons often gives n + 1 lines in a simple first-order case. Exchange, unequal couplings, and second-order effects can invalidate the shortcut.

Substitution and elimination decision guide

Methyl substrates: Usually favorable for SN2 with a suitable nucleophile; no beta carbon means ordinary E2 is unavailable.
Primary substrates: Often SN2 with a good unhindered nucleophile. Bulky strong bases can favor E2 when a beta hydrogen exists.
Secondary substrates: Competition is common. Analyze nucleophile/base strength and size, solvent, and temperature rather than choosing a mechanism from substitution level alone.
Tertiary substrates: Ordinary SN2 is sterically blocked. Strong base often promotes E2; ionizing conditions with weak nucleophiles/bases can allow SN1/E1.
SN2 stereochemistry: Backside attack gives geometric inversion. The written R/S label need not switch because product priority order can change.
SN1 stereochemistry: A planar carbocation can be attacked from both faces; perfect 50:50 racemization is not guaranteed.
E2 geometry: The leaving group and eliminated beta hydrogen usually need an antiperiplanar arrangement; cyclohexane problems often require trans-diaxial groups.
Rearrangements: Consider hydride or alkyl shifts when a carbocation intermediate can form. Concerted SN2 and E2 mechanisms do not involve a free carbocation rearrangement.

This is a study framework, not a guarantee of a single product. See the OpenStax reactivity summary for comparisons.

Reaction families to organize on your own sheet

For each assigned reaction, record starting functional group, reagent, product group, regioselectivity, stereochemistry, mechanism, and exceptions.

Alkane radical halogenation: identify initiation, propagation, and termination.
Alkene additions: distinguish hydrogenation, halogenation, hydrohalogenation, and hydration pathways.
Alkene hydration methods: compare Markovnikov and anti-Markovnikov outcomes and rearrangement possibilities for the actual reagent set.
Alcohol reactions: distinguish proton transfer, substitution, elimination, and oxidation.
Ether reactions: focus on the specific formation and cleavage reactions assigned.
Alkyne reactions: track partial versus complete reduction and the greater acidity of a terminal alkyne relative to an alkane.

Worked examples

Example 1 Formula analysis

For C_{6}H_{10}O, DBE = (2×6 + 2 − 10)/2 = 2. Possibilities include two double bonds, a triple bond, two rings, or a ring plus a double bond. The oxygen could belong to several functional groups. DBE narrows possibilities but does not identify the structure.

Example 2 Acid–base direction

Suppose HA has pKa 5 and HB has pKa 10 in the same solvent. For HA + B^{-} ⇌ A^{-} + HB, K ≈ 10^{5}. Products are favored because the product acid is weaker. That conclusion concerns equilibrium; the numerical rate is a separate question.

Example 3 A simple NMR pattern

An isolated ethyl group often produces a three-proton triplet and two-proton quartet when the only resolved coupling is between CH_{3} and CH_{2}. For ethanol, the OH signal can be broad and exchange-dependent. Use chemical shifts and the molecular formula to distinguish an ethyl group attached to oxygen from other ethyl environments.

Practice questions and answers

DBE for C_{5}H_{10}? 1: one ring or one double bond in the usual model.
Four stereocenters imply exactly 16 stereoisomers? No; 16 is the unconstrained maximum and symmetry can reduce it.
A mixture is 80% R and 20% S. ee? 60% in favor of R.
What happens to a simple SN2 rate if both reactant concentrations double? It increases fourfold.
Is a strong base necessarily the best nucleophile in every solvent? No; sterics and solvent affect nucleophilicity.
Can resonance move an atom to a new position? No; resonance contributors keep atomic connectivity fixed and redistribute electrons.

Review routine

Work in both directions: predict a product from reagents, then suggest a transformation from starting material and product. Explain every arrow and check atoms, charge, and stereochemistry. Build a cumulative error log for missed acid–base steps, wrong electron sources, hidden stereocenters, and overlooked competing mechanisms.