Unit 3 Lecture 1 (1)

1. Classification of Organic Compounds

• IntroductionOrganic Chemistry is focused on the study of structure, properties, composition, and reactions of hydrocarbons and their derivatives, dating back 200-225 years. It specifically examines compounds with covalently bonded carbon atoms.

  • Organic compounds are essential to all living organisms.

  • Examples of hydrocarbons: Methane (CH4), Ethane (C2H6).

Catenation

• Catenation is the capacity of carbon atoms to bond with each other, allowing formation of long chains or rings, which contributes to the vast number of organic compounds.

  • The property happens with elements that have at least a valence of 2.

  • Other elements can catenate, e.g. sulfur and silicon, but to a lesser extent.

Chain Types

• Carbon atoms combine to form:

  • Straight Chains

  • Branched Chains

  • Closed Chains (Rings)

2. Tetravalency

• Tetravalency refers to the property of carbon to form four covalent bonds.

  • With atomic number 6, carbon has an electron configuration of 1s² 2s² 2p², necessitating four electrons in the outer shell.

  • This tetravalent nature results in stable carbon compounds with high versatility in bonding with hydrogen, oxygen, nitrogen, sulfur, etc.

Structural Representation of Organic Compounds

• Primary focus of organic chemistry is on carbon and hydrogen, along with elements like nitrogen, oxygen, halogens, etc.

Complete Structural Formula

• Complete Structure displays atoms, types of bonds, and interconnections. Uses dashes for bonds (single dash for single bonds, double for double bonds).

Condensed Structural Formula

• Condensed Structure is a shortened version, where similar units are grouped using parentheses: Example - CH3(CH2)4CH3.

Bond-line Structural Formula

• Bond-line Structure simplifies representations by omitting hydrogen atoms connected to carbon; zigzag lines represent bonds.

3. Importance of Organic Chemistry

• Organic Chemistry is crucial in daily life, contributing significantly to fields such as medicine, food science, textiles, and energy.

Applications

• Medicines: Synthesis of drug candidates. Examples include Aspirin (anti-migraine) and Ibuprofen (pain relief).

• Food: Enhances flavors and extends shelf life with organic preservatives.

• Clothing: Organic chemistry is vital in textiles, producing fibers like Silk, Nylon, and Cotton.

• Fuels: Hydrocarbons in fossil fuels (coal, oil, natural gas) are essential in daily energy consumption.

4. Classification of Organic Compounds Based on Structure

• Open-Chain Compounds (Acyclic) - Derived from fats, classified as:

  • Straight-Chain (e.g., n-Butane: CH3-CH2-CH2-CH3)

  • Branched-Chain

Closed-Chain Compounds (Cyclic)

• Formed when carbon atoms create rings.

  • Homocyclic (Carbocyclic): Comprised solely of carbon atoms (e.g., Benzene).

  • Heterocyclic: Contains heteroatoms (oxygen, nitrogen, etc.) in the ring (e.g., Furan).

Aromatic Hydrocarbons

• Compounds resembling benzene.

• Benzenoid Aromatic Compounds: Derivatives of benzene (e.g., Naphthalene).

• Non-benzenoid Aromatic Compounds: Different unsaturated rings (e.g., Azulene).

5. IUPAC Nomenclature

• Nomenclature establishes systemic naming conventions to resolve confusion in the naming of organic compounds.

Components of IUPAC Naming

1. Root Word: Indicates the number of carbon atoms in the longest chain.

   • Example roots: Meth, Eth, Prop, But, etc.

2. Suffix: Indicates the functional group.

3. Prefix: Shows side chains or substituents (e.g., methyl, ethyl).

Guidelines for Naming

1. Identify the longest carbon chain.

2. Identify substituents.

3. Assign the main functional group.

4. Number carbon atoms.

5. Combine the names, ensuring proper order.

6. Add prefixes and suffixes as needed.

7. Check for accuracy in final naming.

IUPAC Names of Common Organic Compounds

• Alkanes: CnH2n+2; -ane suffix; Examples: Methane (CH4).

• Alkenes: CnH2n; -ene suffix; Examples: Ethene (C2H4).

• Alkynes: CnH2n-2; -yne suffix; Examples: Ethyne (C2H2).

Compounds with Functional Groups

• Alcohols: R-OH; Suffix -ol.

• Aldehydes: R-CHO; Suffix -al.

• Ketones: RCO-R'; Suffix -one.

• Carboxylic Acids: R-COOH; Suffix -oic acid.

• Esters: RCOOR'; Suffix -oate.

6. Homologous Series

• A homologous series consists of compounds differing by the -CH2- group with a similar functional group.

• Example: Alcohol series (Methyl, Ethyl, Propyl, Butyl).

Characteristics of Homologous Series

1. Share the same general formula.

2. Same functional group.

3. Chemical properties remain consistent across members.

4. Physical properties like boiling point may vary.

7. Functional Group Classification

• Hydrocarbons: Comprises carbon and hydrogen (simplest organic compounds)

• Two types:

  • Aliphatic Hydrocarbons (alkanes, alkenes, alkynes).

  • Aromatic Hydrocarbons (arenes, e.g., Benzene).

8. Compounds Containing Oxygen, Nitrogen, and Sulfur

• Oxygen: Alcohols, Ethers, Aldehydes, Carboxylic Acids.

• Nitrogen: Amines, Nitriles.

• Sulfur: Thiols, Sulfides, and Sulfoxides.

Summary of Classifications

• Compounds may vary greatly based on their functional groups, leading to significant diversity in organic chemistry.