CH 12+13 STUDY NOTES

Introduction to Organic Chemistry

What is Organic Chemistry?

Organic chemistry is the branch of chemistry that studies compounds containing carbon. These compounds are the basis of life and are found in everything from fuels and plastics to pharmaceuticals and biomolecules.

• Organic compounds are primarily made of carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements.

• Examples include methane (CH4), ethanol (C2H5OH), DNA, and proteins.

• Organic chemistry is distinct from inorganic chemistry, which focuses on salts, metals, and non-carbon compounds.

Unique Properties of Carbon

Bonding and Structure

Carbon atoms are unique in their ability to form four covalent bonds, resulting in a vast array of molecular structures.

• Carbon forms four bonds due to its four valence electrons.

• The geometry of methane (CH4) is tetrahedral with bond angles of 109.5°.

• Carbon can bond to other carbons, forming chains, branched structures, and rings.

Example: Methane (CH4) is the simplest organic molecule, with carbon at the center and four hydrogens arranged tetrahedrally.

Adding More Carbons: Alkanes

When more carbons are added, the tetrahedral geometry is maintained (for single bonds).

• Alkanes are saturated hydrocarbons with only single bonds between carbons.

• The first ten alkanes are important to know for nomenclature and structure.

Number of Carbons	Name	Condensed Structural Formula
1	Methane	CH4
2	Ethane	CH3CH3
3	Propane	CH3CH2CH3
4	Butane	CH3(CH2)2CH3
5	Pentane	CH3(CH2)3CH3
6	Hexane	CH3(CH2)4CH3
7	Heptane	CH3(CH2)5CH3
8	Octane	CH3(CH2)6CH3
9	Nonane	CH3(CH2)7CH3
10	Decane	CH3(CH2)8CH3

Types of Hydrocarbons

Alkanes, Alkenes, and Alkynes

• Alkanes: Only single bonds (saturated hydrocarbons).

• Alkenes: Contain at least one double bond between carbons.

• Alkynes: Contain at least one triple bond between carbons.

Example: Ethene (C2H4) is an alkene; ethyne (C2H2) is an alkyne.

Isomerism in Alkenes

Alkenes can have cis-trans isomers (geometric isomers) due to restricted rotation around the double bond.

• Cis isomer: Substituents on the same side of the double bond.

• Trans isomer: Substituents on opposite sides.

• This affects physical properties such as melting and boiling points.

Reactions of Alkenes

Overview

Alkenes are reactive due to the presence of the double bond. Three important reactions are:

• Hydrogenation

• Hydration

• Polymerization

Hydrogenation

Hydrogenation is the addition of hydrogen (H2) to an alkene, converting it to an alkane.

• Requires a metal catalyst (e.g., palladium, platinum, nickel).

• Equation:

$\ce{CH2=CH2 + H2 ->[Pd] CH3-CH3}$

Example: Vegetable oils (alkenes) are hydrogenated to make margarine (alkanes).

Hydration

Hydration is the addition of water (H2O) to an alkene, forming an alcohol.

• Usually requires an acid catalyst (e.g., H+).

• Equation:

$\ce{CH2=CH2 + H2O ->[H^+] CH3CH2OH}$

Example: Ethene reacts with water to form ethanol.

Polymerization

Polymerization is the process where small molecules (monomers) join to form large molecules (polymers).

• Alkenes can undergo addition polymerization.

• Common polymers: polyethylene, polyvinyl chloride (PVC), polystyrene.

Example: Ethene monomers form polyethylene:

$n\ce{CH2=CH2} \rightarrow [-CH2-CH2-]_n$

Aromatic Compounds

Definition and Examples

Aromatic compounds contain a benzene ring (a six-carbon ring with alternating double bonds, delocalized electrons).

• Not all aromatic compounds have a pleasant smell.

• Examples: benzene, toluene, phenol.

Alcohols, Phenols, Thiols, and Ethers

Alcohols

Alcohols are organic compounds containing a hydroxyl group (-OH) attached to a carbon atom.

• General formula: R-OH

• Named using IUPAC nomenclature (e.g., methanol, ethanol, 2-propanol).

• Naming ends in -OL

Phenols

Phenols are aromatic compounds with a hydroxyl group directly attached to a benzene ring.

• Example: phenol, 3-chlorophenol, 4-methylphenol.

• Naming ends in phenol

Thiols

Thiols are similar to alcohols, but contain a thiol group (-SH) instead of a hydroxyl group.

• General formula: R-SH

• Named similarly to alcohols (e.g., methanethiol, ethanethiol).

• Naming ends in Thiol

Ethers

Ethers are compounds with an oxygen atom connected to two alkyl groups by single bonds.

• General formula: R-O-R'

• Examples: diethyl ether, ethoxybenzene.

• Has -ETH or Ether in the name

Reactions of Alcohols and Thiols

Combustion

Alcohols and thiols can undergo combustion, producing carbon dioxide, water, and energy.

$\ce{CH3CH2OH + 3O2 -> 2CO2 + 3H2O + energy}$

Dehydration

Dehydration of alcohols removes water to form alkenes. This is the reverse of hydration.

• Requires acid catalyst and heat.

• Equation:

$\ce{CH3CH2OH ->[H^+, \Delta] CH2=CH2 + H2O}$

Oxidation of Thiols

Thiols can be oxidized to form disulfides, which are important in protein structure.

• Equation:

$\ce{2RSH + [O] -> RSSR + H2O}$

Example: Cysteine residues in proteins form disulfide bonds, stabilizing protein structure.

Oxidation of Alcohols

Alcohols can be oxidized to form carbonyl compounds (aldehydes, ketones, or carboxylic acids).

• Primary alcohols: $\ce{RCH2OH ->[O] RCHO ->[O] RCOOH}$

• Secondary alcohols: $\ce{R2CHOH ->[O] R2CO}$

• Tertiary alcohols: generally resistant to oxidation.

Carbonyl group refers to a C=O functional group, found in several compound classes.

Summary Table: Functional Groups Covered

Functional Group	General Formula	Example
Alcohol	R-OH	Ethanol (CH3CH2OH)
Phenol	Ar-OH	Phenol (C6H5OH)
Thiol	R-SH	Methanethiol (CH3SH)
Ether	R-O-R'	Diethyl ether (CH3CH2OCH2CH3)

Additional info: The notes introduce the foundational concepts of organic chemistry, including structure, nomenclature, and basic reactions of key functional groups, aligning with GOB Chemistry chapters 12 and 13.

RELOOK AT OXIDATION OF ALCOHOLS AND THINOLS

WORK PROBLEMS ON ALL REACTIONS