Alkenes

Addition Reactions of Alkenes

Alkenes are hydrocarbons containing at least one carbon-carbon double bond. Their characteristic reactions are addition reactions, which involve breaking the double bond and adding new atoms to the carbons.

• Hydrogenation: Addition of hydrogen () across the double bond in the presence of a metal catalyst (Pd, Pt, or Ni). - Product: Alkene is converted to an alkane. - Equation:

• Hydration: Addition of water () to the double bond in the presence of a strong acid catalyst (H+ or ). - Product: Alkene is converted to an alcohol. - Markovnikov's Rule: The hydrogen atom adds to the carbon with more hydrogens; the hydroxyl group (OH) adds to the carbon with fewer hydrogens. - Equation:

• Halogenation: Addition of a halogen molecule (, where X = Cl, Br, I) to the double bond. - Product: Alkene is converted to a dihaloalkane (alkane with two halogen atoms added). - Equation:

• Hydrohalogenation: Addition of a hydrogen halide (, where X = Cl, Br, I) to the double bond. - Product: Alkene is converted to a haloalkane. - Markovnikov's Rule: Hydrogen adds to the carbon with more hydrogens; halogen adds to the carbon with fewer hydrogens. - Equation:

Example: Hydration of propene () yields isopropanol ().

Aromatic Compounds

Chemical Properties and Nomenclature

Aromatic compounds contain a benzene ring, which is a stable, cyclic structure with alternating double bonds. When the benzene ring acts as a substituent, it is called phenyl.

• Reactivity: Aromatic compounds do not undergo addition reactions like alkenes. Instead, they undergo substitution reactions, where an atom or group replaces a hydrogen on the ring.

• Example: Bromination of benzene requires and a catalyst (), not just .

Example: The phenyl group is used in naming compounds such as phenylamine (aniline).

Alcohols, Thiols, Phenols, and Ethers

Definitions and Structures

These classes of organic compounds are characterized by specific functional groups:

• Alcohols: Contain a hydroxyl group (OH) single-bonded to a carbon atom.

• Phenols: Contain a hydroxyl group (OH) attached directly to a benzene ring.

• Ethers: Have an oxygen atom bonded to two carbon groups (R-O-R').

• Thiols: Contain a thio group (SH) single-bonded to a carbon atom.

Naming Conventions

• Alcohols: Name by changing the parent alkane name (drop the "e" and add "ol"). Indicate the location of the OH group (e.g., 2-propanol). For cyclic alcohols, the carbon attached to the OH is assumed to be carbon 1.

• Phenols: Follow aromatic compound naming rules; the OH group is always on the benzene ring.

• Ethers:

  • Common Name: Name each carbon chain as a substituent ("yl" ending) in alphabetical order, followed by "ether" (e.g., methyl ethyl ether).

  • IUPAC Name: The smaller chain is named with an "oxy" ending as a substituent; the larger chain is the parent alkane. Indicate the position of the alkoxy group (e.g., 1-methoxypropane).

• Thiols: Add "thiol" to the end of the parent name and indicate the location of the SH group (e.g., 2-propanethiol).

Physical Properties

• Melting/Boiling Points: Highest for alcohols due to hydrogen bonding.

• Solubility: Alcohols have the greatest solubility in water due to hydrogen bonding. Solubility decreases as the number of carbon atoms increases.

Classification of Alcohols

• Primary Alcohols: The carbon with the OH group is attached to one other carbon.

• Secondary Alcohols: The carbon with the OH group is attached to two other carbons.

• Tertiary Alcohols: The carbon with the OH group is attached to three other carbons.

Reactions of Alcohols

• Dehydration: Removal of water from an alcohol in the presence of heat and acid to form an alkene. - Zaitsev's Rule: For secondary alcohols, the hydrogen is removed from the adjacent carbon with the fewest hydrogens. - Equation:

Example: Dehydration of 2-butanol yields 2-butene.

Table: Physical Properties of Alcohols, Phenols, Ethers, and Thiols

Additional info: Table entries inferred from general chemical knowledge.