Introduction to Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds and their properties.
• Carbon's ability to form stable chains and rings of atoms results in a large diversity of organic compounds.

Unique Properties of Carbon

• Carbon has a unique ability to catenate, i.e., to form long chains and cyclic compounds through carbon-carbon bonds.
• Carbon can form single, double, and triple bonds with itself and other elements, leading to structural diversity.
• Carbon commonly forms covalent bonds with hydrogen, oxygen, nitrogen, and halogens in organic molecules.

Hydrocarbons

• Hydrocarbons are organic compounds containing only carbon and hydrogen atoms.
• Alkanes are saturated hydrocarbons with only single bonds.
• Alkenes contain at least one carbon-carbon double bond.
• Alkynes contain at least one carbon-carbon triple bond.
• Aromatic hydrocarbons contain a benzene ring or related structures.

Functional Groups

• Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.
• Alcohols contain an -OH (hydroxyl) group.
• Ethers contain an -O- (alkoxy) group bonded to two alkyl or aryl groups.
• Aldehydes contain a carbonyl group (C=O) bonded to at least one hydrogen atom.
• Ketones contain a carbonyl group (C=O) bonded to two alkyl or aryl groups.
• Carboxylic acids contain a -COOH (carboxyl) group.
• Esters contain a -COOR group.
• Amines contain a nitrogen atom with one or more alkyl or aryl groups attached.
• Amides contain a nitrogen atom attached to a carbonyl group.
• Halides contain a halogen atom (F, Cl, Br, I) bonded to a carbon atom.

Isomers

• Isomers are molecules that have the same molecular formula but different structural arrangements or spatial orientations.
• Structural isomers have the same molecular formula but different connectivity of atoms.
• Stereoisomers have the same connectivity but different spatial arrangement of atoms.
• Enantiomers are stereoisomers that are non-superimposable mirror images of each other (chiral molecules).
• Diastereomers are stereoisomers that are not mirror images of each other.
• Conformational isomers (conformers) are isomers that can be interconverted by rotation around single bonds.

Nomenclature

• The IUPAC (International Union of Pure and Applied Chemistry) nomenclature provides a systematic way to name organic compounds.
• Identify the parent chain, which is the longest continuous carbon chain.
• Number the carbon atoms in the parent chain to give substituents the lowest possible numbers.
• Name and number the substituents.
• Combine the substituent names, numbers, and parent chain name in the correct order.

Reactions

• Addition reactions involve the addition of atoms or groups of atoms to a molecule, typically at a multiple bond.
• Substitution reactions involve the replacement of an atom or group of atoms with another atom or group of atoms.
• Elimination reactions involve the removal of atoms or groups of atoms from a molecule, forming a multiple bond.
• Oxidation reactions increase the number of carbon-oxygen bonds or decrease the number of carbon-hydrogen bonds.
• Reduction reactions decrease the number of carbon-oxygen bonds or increase the number of carbon-hydrogen bonds.

Alkanes

• Alkanes are hydrocarbons with the general formula CₙH₂ₙ₊₂.
• They are saturated hydrocarbons, meaning they contain only single bonds.
• Alkanes are relatively unreactive due to the strength and nonpolarity of C-C and C-H bonds.
• They undergo combustion reactions with oxygen to produce carbon dioxide and water.
• Alkanes can undergo substitution reactions with halogens under UV or heat conditions (halogenation).

Alkenes and Alkynes

• Alkenes are hydrocarbons containing at least one carbon-carbon double bond with the general formula CₙH₂ₙ.
• Alkynes are hydrocarbons containing at least one carbon-carbon triple bond with the general formula CₙH₂ₙ₋₂.
• Alkenes and alkynes are unsaturated hydrocarbons and are more reactive than alkanes.
• They undergo addition reactions readily, such as hydrogenation, halogenation, hydration, and hydrohalogenation.
• Markovnikov's rule states that in the addition of HX to an alkene, the hydrogen atom adds to the carbon with more hydrogen atoms already attached.

Aromatic Compounds

• Aromatic compounds contain a benzene ring or related structures.
• Benzene is a six-membered ring with alternating single and double bonds (C₆H₆).
• Benzene is unusually stable due to delocalization of π electrons in the ring (resonance).
• Aromatic compounds undergo electrophilic aromatic substitution reactions, such as halogenation, nitration, sulfonation, and Friedel-Crafts alkylation and acylation.

Alcohols and Ethers

• Alcohols contain a hydroxyl (-OH) group bonded to an alkyl or aryl group.
• Ethers contain an oxygen atom bonded to two alkyl or aryl groups.
• Alcohols can form hydrogen bonds, resulting in higher boiling points compared to alkanes of similar molecular weight.
• Alcohols can be primary, secondary, or tertiary depending on the number of alkyl groups attached to the carbon bearing the -OH group.
• Ethers are relatively unreactive but can undergo cleavage under strongly acidic conditions.

Aldehydes and Ketones

• Aldehydes contain a carbonyl group (C=O) with at least one hydrogen atom attached to the carbonyl carbon.
• Ketones contain a carbonyl group (C=O) with two alkyl or aryl groups attached to the carbonyl carbon.
• Aldehydes are more reactive than ketones due to less steric hindrance around the carbonyl carbon.
• Aldehydes and ketones undergo nucleophilic addition reactions at the carbonyl carbon.
• They can be reduced to alcohols using reducing agents such as NaBH₄ or LiAlH₄.

Carboxylic Acids

• Carboxylic acids contain a carboxyl group (-COOH), consisting of a carbonyl group and a hydroxyl group.
• They are weak acids and can donate a proton from the carboxyl group.
• Carboxylic acids can form hydrogen bonds, resulting in high boiling points and good solubility in water for small molecules.
• They can react with alcohols to form esters (esterification) under acidic conditions.
• They can be reduced to primary alcohols using strong reducing agents such as LiAlH₄.

Esters

• Esters contain a carbonyl group bonded to an alkoxy group (-COOR).
• They are formed from the reaction of a carboxylic acid and an alcohol (esterification).
• Esters can be hydrolyzed (broken down by water) in acidic or basic conditions to form a carboxylic acid and an alcohol.
• Saponification is the base-catalyzed hydrolysis of esters, producing a carboxylate salt and an alcohol.

Amines and Amides

• Amines contain a nitrogen atom with one, two, or three alkyl or aryl groups attached.
• They can be primary, secondary, or tertiary, depending on the number of alkyl or aryl groups bonded to the nitrogen.
• Amines are basic due to the lone pair of electrons on the nitrogen atom.
• Amides contain a nitrogen atom bonded to a carbonyl group (-CONR₂).
• Amides are formed from the reaction of a carboxylic acid and an amine.
• Amides are less basic than amines due to the delocalization of the nitrogen lone pair onto the carbonyl group.

Chirality

• A chiral molecule is a molecule that is non-superimposable on its mirror image.
• A chiral carbon (stereocenter) is a carbon atom bonded to four different groups.
• Enantiomers are pairs of chiral molecules that are mirror images of each other.
• Optical activity is the ability of chiral molecules to rotate plane-polarized light.
• A racemic mixture is a mixture containing equal amounts of both enantiomers, resulting in no net optical rotation.