Unit 3 Organic Chemistry. Chemistry 2202. Introduction. Organic Chemistry is the study of the molecular compounds of carbon. eg. CH 4 CH 3 OH CH 3 NH 2 Organic compounds exclude oxides of carbon and ions containing carbon. ie. CO, CO 2 , KCN, CaCO 3
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Introduction • Organic Chemistry is the study of the molecular compounds of carbon. eg. CH4 CH3OH CH3NH2 • Organic compounds exclude oxides of carbon and ions containing carbon. ie. CO, CO2, KCN, CaCO3 are NOT organic compounds!!
History of Organic Chemistry • Organic chemistry can be traced back to ancient times when medicine men extracted chemicals from plants and animals to treat members of their tribes • Organic chemistry was first defined as a branch of modern science in the early 1800's by Jon Jacob Berzelius
Berzelius believed in Vitalism - organic compounds could only originate from living organisms through the action of some vital force • organic compounds originate in living or once-living matter • inorganic compounds come from "mineral" or non-living matter
The huge number of organic compounds is due mainly to the ability of carbon atoms to form stable chains, branched chains, rings, branched rings, multiple rings, and multiple bonds (double and triple bonds) to itself and to many other non-metal atoms.
Sources of Organic Compounds 1. Carbonized Organic Matter - fossil fuels such as coal, oil, and natural gas - basis for the petrochemical industry 2. Living Organisms eg: - penicillin from mold - ASA from the bark of a willow tree
3. Invention - antibiotics, aspirin, vanilla flavoring, and heart drugs are manufactured from organic starting materials - plastics
Structural Isomers • Structures that have the same molecular formula but different structural formulas are called structural isomers eg. C4H10 Practice: Draw all structural isomers of C5H12 and C6H14
Structural Isomers • structural isomers have the same chemical formula but have different chemical and physical properties.
Alkyl Groups • An alkyl group has one less hydrogen than an alkane. • General Formula: CnH2n + 1 • To name an alkyl group, use the prefix to indicate the # of carbon atoms followed by the suffix –yl eg. -C7H15 heptyl
Alkyl Groups methyl -CH3 ethyl -C2H5 or -CH2CH3 propyl -C3H7 or -CH2CH2CH3
Alkyl Groups • Branched alkanes are alkanes that contain one or more alkyl groups eg.
Naming Branched Alkanes • Find the longest continuous chain of carbons and name it using the alkane name. This is the parent chain. • Number the carbons in the parent chain starting from the end closest to branching. These numbers will indicate the location of alkyl groups.
Naming Branched Alkanes • List the alkyl groups in alphabetical order. Use Latin prefixes if an alkyl group occurs more than once. (di = 2, tri = 3, tetra = 4, etc.) • Use a number to show the location of each alkyl group on the parent.
Naming Branched Alkanes • Use commas to separate numbers, and hyphens to separate numbers and letters.
Alkenes and Alkynes • saturated compounds contain only single bonds between carbon atoms eg. alkanes • saturated compounds have the maximum number of hydrogen atoms bonded to carbon atoms
Alkenes and Alkynes • unsaturated compounds contain double or triple bonds between carbon atoms eg. alkenes and alkynes
Naming Alkenes and Alkynes • Name the longest continuous chain that contains the double/triple bond. Use the smallest possible number to indicate the position of the double or triple bond.
Naming Alkenes and Alkynes • Branches are named using the same rules for alkanes. Number the branches starting at the same end used to number the multiple bond.
Aromatic Compounds • Aromatic hydrocarbons contain at least one benzene ring. • The chemical formula for benzene, C6H6 , was determined by Michael Faraday in 1825. • Structural formula was determined by August Kekulé in 1865.
Aromatic Compounds • benzene ring consists of six carbon atoms, each of which is bonded to a hydrogen atom (Try to draw this!!) • C6H6 can be drawn with alternating single and double bonds.
Aromatic Compounds • While C=C double bonds are shorter than C-C single carbon bonds, x-ray crystallography shows that all six C-C bonds in benzene are the same length. • Benzene molecules behave like alkanes in chemical reactions, not like the alkenes
Aromatic Compounds • Kekulé thought benzene could exist in two forms and used the idea of resonance to explain its structure. • The resonance structure is an average of the electron distributions.
Aromatic Compounds • bonding electrons that were thought to be in the double bonds are delocalized and shared equally over the 6 carbon atoms • the bonds in benzene are like “1 ½” bonds – somewhere between single and double.
Naming Aromatic Compounds • an alkyl benzene has one or more H atoms replaced by an alkyl group. • name the alkyl groups, using numbers where necessary, followed by the word benzene.
