1. Carbon: Not Just Another Element
Chapter 23

2. Learning Objectives Students understand
General principles of structure and bonding applied to organic compounds
Why carbon forms a vast array of diverse chemical compounds
Students will be able to
Classify organic compounds based on formula and structure
Recognize and draw structures of structural isomers and stereoisomers for carbon compounds
Draw structures of molecules, given the name and/or the formula, and name organic compounds using standard nomenclature rules

3. 23.1 Why Carbon?
Organic compounds contain the element carbon, which can bond with other carbon atoms to form straight chains and branched chains.
Isomers
identical composition but linked in different ways

4. 23.2 Hydrocarbons
Carbon and hydrogen only
Alkanes, cycloalkanes
Alkenes
Alkynes
Aromatic compounds

5. Alkanes Alkanes contain only single bonds between carbon atoms.
Alkanes and other organic compounds are best represented by structural formulas and can be named using systematic rules determined by the International Union of Pure and Applied Chemistry (IUPAC).

6. Alkanes
Each alkane has the general formula CnH2n+2; n is the number of carbon atoms.
Straight-chain hydrocarbons, also called unbranched or normal, all carbon atoms are connected in a long chain.
The name of each alkane ends in the suffix “-ane”.

7. Alkanes
The root of the name corresponds to the longest carbon chain in the compound
Substituent groups are identified by a name and position in the carbon chain
called alkyl group
2 or more of the same alkyl group (use di-,tri- tetra-) otherwise list in alphabetical

8. Name
Formula
Methane
CH4
Hexane
C6H14
Ethane
C2H6
Heptane
C7H16
Propane
C3H8
Octane
C8H18
Butane
C4H10
Nonane
C9H20
Pentane
C5H12
Decane
C10H22

9. Saturated Compounds
Saturated hydrocarbons have all carbon-carbon single bonds.
Unsaturated hydrocarbons contain carbon-carbon multiple bonds.

10. Cyclic Alkanes and Alkane Properties
Alkanes that contain hydrocarbon rings are called cyclic alkanes.
Alkanes are nonpolar compounds that have low reactivity and lower melting points and boiling points (weak C-C bonds – strained hydrocarbons) than polar molecules of similar size and mass.

11. Alkenes and Alkynes
Alkenes and alkynes are hydrocarbons that contain at least one double or triple bond, respectively.
Alkenes and alkynes are nonpolar compounds with greater reactivity than alkanes but with other properties similar to alkanes.

12. Alkenes and Alkynes
Alkenes and alkynes can also be named using IUPAC rules.
Look at the longest chain to figure out the “parent name”.
Alkenes have the general formula of CnH2n.
Root ending is “-ene”
Alkynes have the general formula of CnH2n-2.
Root ending is “-yne”

13. Naming Isomers
Look at the longest continuous chain that determines the root name. This is the last part of the name.
Next name the alkyl group that substitutes on the parent chain.
Specify the location of the groups by numbering longest chain sequentially.
hexane vs. 2-methylpentane vs. 2,3 – dimethylbutane vs. 2,2 - dimethylbutane

14. Naming Isomers
Alkenes exhibit cis-trans isomerism because rotation around the double bond is restricted.
In cis isomerism the heavier groups are on the same side of the double bond.
In trans isomerism the heavier groups are on opposite sides of the double bond.

15. cis – 2-pentene
trans-2-pentene

16. Aromatic Hydrocarbons and Petroleum
Aromatic hydrocarbons contain benzene rings as part of their molecular structures. Nonaromatic hydrocarbons are called aliphatic hydrocarbons.
Extra stability due to resonance stabilization

17. Aromatic Hydrocarbons
May contain two or more benzene rings fused together
Some are carcinogenic
Major sources are petroleum and natural gas
Fractional distillation can separate petroleum into components

18. 23.3-23.4 Functional Groups Halide Alcohol R-OH Ether R-O-R’
Aldehyde R-(C=O)-H
Ketone R-(C=O)-R
Carboxylic acid R-(C=O)-OH
Ester R-(C=O)-O-R’
Amide R-NH2, R-NHR’, R-NR’R
Amine H-NH2, H-NHR’, H-NR’R