Structure and Functional Groups, Intermolecular Forces and Infrared (IR) Spectroscopy

Hydrocarbons: Representative Carbon-carbon formed the most strongest bond in organic molecules Hydrocarbon: molecules that contain only H & C

Alkanes Principle sources are natural gas and petroleum Saturated hydrocarbons No double or triple bonds General formula: C n H 2n+2 E.gCH 4 C 2 H 6 C 3 H 8

Methane gas Produces carbon dioxide and hydrogen when burning

Methane

Alkenes Unsaturated hydrocarbons: contain double bonds General formula: C n H 2n Used widely in the industry Some occurs as plant hormone Involved in the ripening process

Alkenes Structure of ethene

Alkynes Unsaturated hydrocarbon with at least one triple bond General formula: CnH2n-2 Use for biosynthesis

Alkynes Ethyne

Benzene Six membered ring with alternating single bonds

Polar and NonPolar Molecules Diatomic molecules with different polarity is a polar molecules Vectors cancelled out  non polar Dipole moment = charge (in esu) x distance (cm) Must know 3-D structure

Examples

Using a three dimensional formula, show the direction of the dipole moment of CH 3 OH. Write ∂ - and ∂ + signs next to the appropriate atoms

Functional Groups Part of a molecule where most of its chemical reaction occur Defined by characteristic arrangements of atoms Determined the compound’s chemical properties

2.5 Alkyl and the symbol R # CN1ameAlkyl (one H has removed) 1MethaneMethyl 2EthaneEthyl 3PropanePropyl 4ButaneButyl 5PentanePentyl 6HexaneHexyl 7HeptaneHeptyl 8OctaneOctyl 9NonaneNonyl 10DecaneDecyl

Functional groups Alkyl groups are designated as R General formula : R-H

Phenyl and Benzyl groups When benzene group is attached to some other groups of atoms in molecule, it is called phenyl Abbreviated as Ar

Phenyl and Benzyl groups The combination of a phenyl group and methylene group ( -CH 2 -) is called benzyl group

2.6 Alkyl Halides or haloalkanes Alkyl halides are compounds in which a halogen atom is replaced with a hydrogen atom from alkane Also known as haloalkanes General formula: R-X X = fluorine, chlorine, bromine and iodine CH 3 Cl - chloromethane

Alkyl Halides Classified as being Primary (1 o ) Secondary (2 o ) Tertiary (3 o )

Examples Write bond-line structure for a. An alkane with formula C 5 H 12 that has no secondary or tertiary carbon atoms b. A secondary alkyl bromide with formula C4H9Br c. Two constitutionally isomeric primary alky bromide

Alcohols Hydrocarbons that contain hydroxyl group (OH) Attached to an sp 3 -hybridized carbon

Alcohols Classified as Primary (1 o ) Secondary (2 o ) Tertiary (3 o )

Examples Write bond-line structure formulas for a. Two primary alcohols b. A secondary alcohols All having the molecular formula C 4 H 10 O