CHE 251-003 Organic Chemistry I - Fall 2025 Syllabus and Study Guide

CHE 251-003 Organic Chemistry I - Fall 2025

Course Overview

This course is the first half of a one-year sequence exploring the chemistry of carbon compounds. It covers fundamental concepts such as nomenclature, structure, bonding, reactivity, and the properties of major classes of organic compounds, with a focus on functional group chemistry and reaction mechanisms.

Course Learning Goals

Basic Structure of Organic Molecules

• Definition: Organic molecules are primarily composed of carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements.

• Key Concepts:

  • Drawing appropriate numbers of lone pairs on organic molecules.

  • Assigning formal charges using Lewis or stick structures.

  • Predicting the shape and hybridization of atoms in organic molecules.

  • Converting between Lewis structures and line-angle (stick) representations.

• Example: Drawing the Lewis structure of ethanol and converting it to a line-angle formula.

Polarity and Intermolecular Forces

• Definition: Polarity refers to the distribution of electrical charge over the atoms joined by the bond. Intermolecular forces are forces of attraction or repulsion between molecules.

• Key Points:

  • Drawing dipole moments and partial charges on molecules.

  • Identifying and ranking types of intermolecular forces (e.g., hydrogen bonding, dipole-dipole, London dispersion).

  • Predicting which forces dominate in a given molecule.

• Example: Water exhibits strong hydrogen bonding due to its polar O-H bonds.

Acid/Base Chemistry

• Definition: Acids are proton donors, and bases are proton acceptors. The strength of acids and bases is often measured by their pKa values.

• Key Points:

  • Stating the approximate pKa value for a given hydrogen atom in an organic molecule.

  • Ranking acidity or basicity of organic compounds based on resonance, size, electronegativity, hybridization, and inductive effects.

• Formula: $\text{p}K_a = -\log_{10} K_a$

• Example: Carboxylic acids (pKa ~ 5) are more acidic than alcohols (pKa ~ 16).

Alkane, Cycloalkane, and Alkene Structure and Naming

• Definition: Alkanes are saturated hydrocarbons, cycloalkanes are ring-shaped alkanes, and alkenes contain at least one carbon-carbon double bond.

• Key Points:

  • Naming alkanes, cycloalkanes, haloalkanes, and alkenes using IUPAC rules.

  • Drawing Lewis or stick structures for these compounds.

  • Drawing cyclohexane in its chair conformation with correct substituent placement.

  • Labeling alkenes as E, Z, or neither based on the Cahn-Ingold-Prelog priority rules.

• Example: 2-bromopropane, cis-2-butene, and cyclohexane chair conformer with axial/equatorial substituents.

Stereochemistry

• Definition: Stereochemistry is the study of the spatial arrangement of atoms in molecules and its effect on their chemical behavior.

• Key Points:

  • Identifying all chiral (stereogenic) centers in a molecule.

  • Labeling chiral centers as R or S using the Cahn-Ingold-Prelog system.

  • Determining relationships between molecules: constitutional isomers, enantiomers, diastereomers, or identical.

• Example: 2-butanol has one chiral center and exists as two enantiomers (R and S).

Reaction Intermediates and Organic Reactions

• Definition: Reaction intermediates are short-lived species formed during the conversion of reactants to products.

• Key Points:

  • Identifying primary, secondary, tertiary, allylic, and benzylic intermediates (radical, carbocation, carbanion).

  • Drawing reaction-energy diagrams showing reactants, products, transition states, activation energies, and intermediates.

  • Ranking intermediates by stability.

• Example: Tertiary carbocations are more stable than secondary or primary carbocations.

Radical Halogenation of Alkanes

• Definition: Radical halogenation is a reaction where alkanes react with halogens (e.g., Cl2, Br2) under light or heat to form haloalkanes.

• Key Points:

  • Predicting the major product based on the stability of radical intermediates.

  • Describing the mechanism: initiation, propagation, and termination steps.

• Example: Chlorination of methane yields chloromethane and hydrogen chloride.

Nucleophilic Substitution Reactions (SN1 and SN2)

• Definition: Nucleophilic substitution reactions involve the replacement of a leaving group by a nucleophile. SN1 is unimolecular, SN2 is bimolecular.

• Key Points:

  • Identifying nucleophiles, electrophiles, and leaving groups.

  • Ranking reactions by rate based on substrate structure and reaction conditions.

  • Using curved arrows to show electron movement.

• Example: Hydrolysis of tert-butyl chloride (SN1) vs. methyl bromide (SN2).

• Formula: $\text{Rate}_{\text{SN1}} = k[\text{R-L}]$ $\text{Rate}_{\text{SN2}} = k[\text{R-L}][\text{Nu}^-]$

Elimination Reactions (E1 and E2)

• Definition: Elimination reactions result in the removal of atoms or groups from a molecule, forming a double bond. E1 is unimolecular, E2 is bimolecular.

• Key Points:

  • Predicting the major elimination product based on Zaitsev's rule (the more substituted alkene is favored).

  • Drawing mechanisms for both E1 and E2 reactions.

  • Identifying reaction conditions that favor elimination over substitution.

• Example: Dehydrohalogenation of 2-bromobutane yields 2-butene (major) and 1-butene (minor).

Electrophilic Addition Reactions to Alkenes

• Definition: Electrophilic addition reactions involve the addition of an electrophile and a nucleophile across a double bond.

• Key Points:

  • Predicting major products of acid-mediated electrophilic addition to alkenes (e.g., HBr, H2O, ROH).

  • Drawing mechanisms for acid-catalyzed hydration and halogenation.

  • Predicting regioselectivity and stereochemistry of the product.

  • Predicting the product from the addition of X2 or X2/H2O to an alkene.

  • Predicting the product for epoxidation of an alkene.

• Example: Addition of HBr to propene yields 2-bromopropane (Markovnikov product).

Course Structure and Assessment

Prerequisites

• CHE 111 (General Chemistry I)

• CHE 112 (General Chemistry II)

• Corequisite: CHE 253 (Organic Chemistry Lab I)

• Minimum grade of C- in all prerequisite courses.

Assignments and Grading

• Online Homework: 5%

• Pop Quizzes: 10%

• In-Class Exams: 65% (three 75-minute exams, lowest dropped)

• ACS Final Exam: 20% (cumulative, standardized exam)

Grading Scale

Grade	Percentage
A	93.3-100
A-	90-93.2
B+	86.7-89.9
B	83.3-86.6
B-	80-83.3
C+	76.7-79.9
C	73.3-76.6
C-	70-73.3
D+	66.7-69.9
D	63.3-66.6
F	< 60

Additional Course Policies and Resources

• Academic Integrity: Plagiarism, unauthorized collaboration, and use of generative AI without proper citation are prohibited.

• Disability Accommodations: Contact the Student Access Office for support.

• Student Counseling: Confidential mental health resources are available.

• Attendance: Required for all registered students; make-up policies apply for excused absences.

• Religious Observance: Notify the instructor in advance for accommodations.

• Diversity Statement: The College of Arts and Sciences values diversity, equity, and inclusion.

Weekly Topics Overview

Week	Topic
1	Structure and bonding, functional groups
2	Conformations and resonance
3	Acids and bases, charge distribution
4	Alkane structure and nomenclature
5	Stereochemistry in alkanes
6	Stereochemistry in alkenes
7	Substitution and elimination reactions
8	Regiochemistry in reactions
9	Oxidation, epoxidation, and epoxide opening
10	Oxidation and aromatic compounds
11	Reduction mechanisms
12	Protecting groups and tosylations
13	NMR and mass spectrometry
14	Alkyne reactions
15	Review and final exam preparation

Additional info: This syllabus provides a comprehensive overview of the foundational topics in Organic Chemistry I, including structure, reactivity, and mechanisms, as well as course policies and resources for student success.