OCHEM 8A: lecture 1

Organic Chemistry Course Outline

Introduction

• Welcome and introductions of session participants: Darsha, Kalise, Sean

• Discussion of LSS tutoring support

Supporting Resources

• Tutoring

  • Kalise: fourth-year chemistry major, 2 years tutoring experience.

  • Priority sign-ups: Wednesday; regular sign-ups: Friday.

  • Free tutoring sessions encouraged.

• ACE Support

  • Application needed, information available upon request.

• Organic Chemistry Learning Center

  • Location: PSP 335, open Mon-Fri, 8 AM - 5 PM.

  • Resources available: whiteboards, textbooks, models, handouts.

Course Logistics

• Office Hours

  • Available on Wednesdays and Fridays for one-on-one support.

  • Sign-up through Canvas.

• Course Materials

  • Textbook: "Organic Chemistry Principles and Mechanisms" by Joel Carty.

  • Accessible via Inclusive Access, $53.75 for the quarter.

  • Opt-out instructions available on Canvas by January 24.

  • Course notes: $15.88 from copy center, recommended for class note-taking.

Canvas Overview

• Learning Environment

  • Canvas is primary source for recordings, assignments, resources.

  • First assignment due tomorrow to assess readiness.

• Assignments and Grading

  • Quizzes: open for one week, no time limit.

  • No penalty for wrong answers in SmartWork; limited attempts, lowest score dropped.

  • Discussion attendance: counts for 6% of final grade.

  • Exams: two midterms, one final, no make-ups available.

Key Course Topics

• Organic Chemistry Themes

  • Fundamental principles; structure and function; problem-solving essential.

Lewis Structures

• Definition:

  • Lewis structures are graphical representations used to depict the arrangement of atoms in a molecule, along with the distribution of valence electrons. They help visualize how atoms bond to form molecules and provide insights into the molecule’s geometry and reactivity.

• Steps to Draw Lewis Structures:

  1. Count Total Valence Electrons:

     • Calculate the total number of valence electrons for all atoms in the molecule (considering group number on the periodic table).

  2. Arrange Atoms:

     • Identify a central atom (usually the least electronegative element) and arrange other atoms around it, connecting with single bonds.

  3. Satisfy the Octet Rule:

     • Distribute remaining electrons to achieve octets for the surrounding atoms (or duplets for hydrogen) by placing electrons in pairs (dots).

  4. Form Multiple Bonds:

     • If necessary, convert lone pairs from surrounding atoms into double or triple bonds to satisfy the octet rule for the central atom.

  5. Check Formal Charges:

     • Adjust the structure if needed by changing bond types to minimize formal charges on atoms.

• Importance of Lewis Structures:

  • They provide a framework to predict molecular shape, reactivity, and polarity. Understanding the Lewis structure is crucial for grasping the concepts of resonance, hybridization, and molecular orbital theory.

Formal Charges

• Definition:

  • A formal charge is a theoretical charge assigned to an atom in a molecule to understand its electron distribution. It reflects how many electrons an atom would own if all bonds were perfectly covalent (shared equally between atoms).

• Formula:

  [\text{Formal Charge} = \text{Valence Electrons} - \text{Non-Bonding Electrons} - \frac{1}{2} \text{Bonding Electrons}]

  • Where:

    • Valence Electrons are the total electrons in the atom's outer shell.

    • Non-Bonding Electrons are electrons that are not involved in bonding (lone pairs).

    • Bonding Electrons are electrons involved in covalent bonds with other atoms.

• Significance:

  • Assessing formal charges is crucial for determining the most stable structure of a molecule. A stable molecule tends to have formal charges close to zero for most atoms, leading to lower energy configurations. Structures that minimize formal charges are often the most reliable representation of the actual molecule.

  • Additionally, formal charges play a significant role in understanding reactivity and reaction pathways in organic chemistry.

Learning Strategies

• Attend class, engage with material, pace study effectively.

• Expectation: 15 hours/week for a five-credit course.

• Develop critical thinking for complex material analysis.

Conclusion

• Final Notes

  • Use available resources and ask questions.

• Reflection on Learning

  • Urged to reflect on challenges and develop overcoming strategies throughout the course.