Chapter 20 Carbon and Hydrocarbons n n 20

Chapter 20: Carbon and Hydrocarbons n n 20. 1 – Abundance and Importance of Carbon 20. 2 – Organic Compounds 20. 3 – Saturated Hydrocarbons 20. 4 – Unsaturated Hydrocarbons

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

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

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

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

Carbon Bonding to Other Elements n n 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 n Isomer – Compounds that have the same molecular formula but different structures n As the number of carbons increases so does the number of possible isomers

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

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

Isomers - Geometric n n 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 n Hydrocarbons in which each carbon atom in the molecule form four single covalent bonds with other atoms

Alkanes n n n Cn. H 2 n+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 n Alkanes in which the carbon atoms are arranged in a ring, or cyclic, structure

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

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

Example

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

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

Example n Draw 1, 1 - dimethylcyclobutane

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

Alkenes n Cn. H 2 n Hydrocarbons that contain double covalent bonds

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

Example

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

Example n Name the following

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

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

Example n Name the following

Example