Chapter 20: Carbon and Hydrocarbons 20.1 – Abundance and Importance of Carbon 20.2 – Organic Compounds 20.3 – Saturated Hydrocarbons 20.4 – Unsaturated Hydrocarbons

Structure and Bonding of Carbon Carbon, the first member of Group 14, has mostly nonmetallic properties. Carbon atoms tend to form four single bonds. This bonding results in a tetrahedral shape.

Allotropes of Carbon Carbon occurs in several solid allotropic forms that have dramatically different properties. Diamond – Colorless, crystalline, solid form of carbon Graphite – soft, black, crystalline form of carbon that is a fair conductor of electricity. Fullerenes – dark colored solids made of spherically networked carbon atom cages

Allotropes of Carbon - Diamond The hardest material known to man Carbon atoms are bonded covalently in a network fashion Conducts heat 5x better than silver or copper Does not conduct electricity

Allotropes of Carbon - Graphite Soft, crumbles easily and feels greasy Used as a lubricant and as lead Good conductor of electricity Stronger and lighter than steel

Allotropes of Carbon - Fullerenes Discovered in the 1980s (N.P. 1996) Structure consists of near spherical cages Scientists are currently trying to find practical uses for these substances

Organic Compounds Covalently bonded compounds containing carbon, excluding carbonates and oxides The diversity of organic compounds results from the uniqueness of carbon’s structure and bonding

Carbon – Carbon Bonding Catenation – Carbon atoms are unique in their ability to form long chains and rings of covalently bonded atoms.

Carbon Bonding to Other Elements Hydrocarbons – composed of only carbon and hydrogen; they are the simplest organic compounds. Most contain hydrocarbon backbones and have other elements added on (O, S, and N)

Arrangement of Atoms Isomer – Compounds that have the same molecular formula but different structures As the number of carbons increases so does the number of possible isomers

Structural Formula Indicates the number and types of atoms present in a molecule and also shows the bonding arrangement of the atoms Structural formulas do not accurately represent the three dimensional shape of the molecule.

Isomers – Structural Structural Isomers – isomers in which the atoms are bonded together in different orders

Isomers - Geometric Isomers in which the order of atom bonding is the same but the arrangement of atoms in space is different In order for geometric isomers to exist, there must be a rigid structure in the molecule to prevent free rotation around a bond

Cis and Trans

Saturated Hydrocarbons Hydrocarbons in which each carbon atom in the molecule form four single covalent bonds with other atoms

Alkanes CnH2n+2 Hydrocarbons that contain only single bonds Homologous series – one in which adjacent members differ by a constant unit. Alkyl groups- groups of atoms that are formed when one hydrogen atom is removed from an alkane molecule

Cycloalkanes Alkanes in which the carbon atoms are arranged in a ring, or cyclic, structure

Alkane Nomenclature Unbranched Chain Count the longest continuous chain. Use greek prefix (at right) End with -ane

Alkane Nomenclature Branched Chain Name the longest chain (See previous) Add the name of the alkyl group Insert position numbers Punctuate

Example

Cycloalkane Nomenclature Name the longest chain Add Cyclo- Add names of alkyl groups Number the carbons (lowest numbers) Inset position numbers Punctuate

Example Give the name of the following molecule 6 carbons = hexane CH3 = methyl Number around the circle 1,3 - dimethlycyclohexane

Example Draw 1,1- dimethylcyclobutane

Unsaturated Hydrocarbons Hydrocarbons in which not all carbon atoms have four single covalent bonds

Alkenes CnH2n Hydrocarbons that contain double covalent bonds

Alkene Nomenclature Name the same as Alkane Locate the longest continuous chain that contains the double bond(s). Double bond should have lowest number

Example

Alkynes CnH2n-2 Hydrocarbons with triple covalent bonds Named the same as others Find the longest chain containing a triple bond Number so triple bond has lowest number

Example Name the following

Aromatic Hydrocarbons Hydrocarbons with six membered carbon rings and delocalized electrons Benzene – the primary aromatic hydrocarbon

Aromatic Nomenclature Name the parent Hydrocarbon (Usually benzene) Name the Alkyl groups Number the carbon atoms Insert position numbers Add Punctuation

Example Name the following

Example