Organic Chemistry 1 - CHEM 2310 Lecture Notes

Organic Chemistry I - CHEM 2310 Notes

Introduction

  • Course Title: Organic Chemistry 1
  • Course Code: CHEM 2310
  • Instructor: Dr. Ranga Don
  • Institution: Weber State University

Key Concepts

Protons and Acids

  • When referring to a proton, it always denotes H+.
    • H consists of one electron and one proton (1st row, 1st group).
    • Removal of an electron results in H+, which is considered a nucleus with one proton.
  • Acids are defined as proton donors.
  • Bases are defined as proton acceptors.

Hydrogen Bonding and Acidity

  • The polarization of the H-A bond influences the acidity:
    • More polarized H-A bonds are easier to break.
    • Easier proton donation indicates higher acidity (lower pKa).
    • Key Message:
      • The more polarized the H-A bond, the more acidic the molecule can be.
    • Reaction Example:
      • H-A → H+ + A-

Inductive Effects on Acidity

Acidity Hierarchy

  • Organic molecules assessed include:
    • Iodoacetic Acid: pKa = 3.2
    • Acetic Acid: pKa = 4.76
    • Butanoic Acid: pKa = 4.82
    • Bromoacetic Acid: pKa = 2.9
    • Chloroacetic Acid: pKa = 2.8
    • Dichloroacetic Acid: pKa = 1.3
    • Fluoroacetic Acid: pKa = 2.7
    • Trichloroacetic Acid: pKa = 0.6
  • Patterns observed:
    • As the acidity increases, the pKa values decrease.

Factors Affecting Acidity

  • Influence of electronegative groups on acidity:
    1. Electronegativity of the bonded group.
    2. Number of electronegative groups attached.
    3. Distance of the electronegative group from the acidic proton.

Electron Withdrawing Groups (EWG)

  • Definition: Groups that reduce electron density in a molecule by pulling electrons through the carbon atom they bond to.
  • Examples of Electron Withdrawing Groups:
    • Nitro group: (-NO2)
    • Aldehydes: (-CHO)
    • Ketones: (-C=OR)
    • Cyano groups: (-CN)
    • Carboxylic acids: (-COOH)
    • Esters: (-COOR)

Hybridization Effects on Acidity

  • Hybridization and acidity:
    • sp³ hybridization (25% s character): Less acidic.
    • sp² hybridization (33% s character): Increased acidity.
    • sp hybridization (50% s character): Most acidic.
  • Key Observations:
    • Protons bonded to sp-hybridized carbon atoms are significantly more acidic compared to those bonded to sp³ carbon atoms.

Functional Groups

Definition

  • Functional group: A group of atoms within a molecule that has characteristic chemical behavior.

Importance of Functional Groups

  • Functional groups facilitate the classification of compounds into families based on structural features.

Classification of Functional Groups with Carbon Bonds

  1. Carbon-Carbon Multiple Bonds:
    • Alkenes: Double bonds
    • Alkynes: Triple bonds
    • Arenes: Alternating double and single bonds in a six-membered carbon ring
  2. Common Functional Groups (Table 3.1):
    • Alkene: H2C=CH2 (Ethene)
    • Alkyne: HC≡CH (Ethyne)
    • Amine: CH3NH2 (Methylamine)
    • Alcohol: CH3OH (Methanol)
    • Aldehyde: CH3CHO (Ethanal)
    • Ketone: CH3C(O)CH3 (Propanone)
    • Carboxylic Acid: CH3COOH (Ethanoic Acid)

Classification of Hydrocarbons

  • Hydrocarbons are classified based on bonding:
    • Alkanes: Saturated hydrocarbons containing only single bonds.
    • Formula for alkanes: CnH{2n+2}
    • First six unbranched alkanes are named: Methane, Ethane, Propane, Butane, Pentane, Hexane.

Nomenclature of Alkanes

General Rules

  1. Identify the longest continuous carbon chain.
  2. Number the chain from the end nearest a substituent.
  3. Name substituent groups as alkyl groups (substitute -ane with -yl).
  4. Organize multiple substituents by location and type.

Examples of Nomenclature

  • Naming instances:
    • Longest chain: Identify the main chain and its substituents.
    • Example:
      • 4-Ethyl-2,2,3,6-tetramethyloctane follows the systematic naming rules

Common Alkyl Groups

  • Special names for common alkyls to memorize:
    • Isopropyl (isobutane)
    • Isobutyl, Sec-butyl, Tert-butyl
  • Different alkyl group structures are identified based on branching and location.

Haloalkanes

  • Haloalkanes: Named similarly to alkanes, with halogen atoms treated as substituents.
    • Naming for halogen substituents:
      • F = fluoro-
      • Cl = chloro-
      • Br = bromo-
      • I = iodo-

Carbon Study Terms for Classification

  • Features of carbon in hydrocarbons categorized as primary (1°), secondary (2°), or tertiary (3°) based on attachment.
    • Illustrations indicating the form of carbon attachments in alkyl groups.

Conclusion

  • Engagement in group activities for reinforcing concepts discussed.
  • Positive mindset encouraged throughout the learning process.