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| Home | | CHM151 | | Course Policy | | Office Hours | | WebCT Quiz | | Lab Write-up | | Useful Websites | | Your Instructor | Organic Chemistry Lecture Notes Objectives: After the completion of this chapter you should be able to - a) name hydrocarbons (alkanes, alkenes, alkynes, aromatics); b) name alcohols, phenols, ethers, and amines; c) name acids, aldehydes, ketones, and ethers; d) identify alkanes, alkenes, alkynes and aromatics from structural formulas; e) identify acids, aldehydes, ketones, and esters from structural formulas; f) identify alcohols, phenols, ethers, and amines from structural formulas; g) identify general formulas of organic compounds; h) answer alcohol related questions; and i) define/identify miscellaneous terms. Organic chemistry: (Chemistry of carbon) The definition of organic chemistry has changed over the years showing the dynamic character of science. Until the nineteenth century, chemists believed that organic chemicals are related to living things. This all changed in 1828, when Friedrich Wohler synthesized the organic compound urea (found in urine) from ammonium cyanate. Organic chemistry is now defined as the chemistry of carbon-containing compounds. Carbon atoms are unique in their ability to bond to each other so strongly that they can form long chains, branches and rings of various sizes. Carbon can also bond strongly to other atoms such as hydrogen, oxygen, nitrogen, sulfur, and halogens. Carbon forms millions of compounds. Hydrocarbons: The simplest organic compounds are hydrocarbons, which contain only hydrogen and carbon. Hydrocarbons are classified according to the type of bonding between carbon atoms. Alkanes: Alkanes contain carbon-to-carbon single bonds only. The general formula is CnH2n+2. Following is a list of the first ten members that you need to memorize. Name Molecular formula Condensed structural formula Methane CH4 CH4 Ethane C2H6 CH3–CH3 Propane C3H8 CH3–CH2–CH3 Butane C4H10 CH3CH2CH2CH3 Pentane C5H12 CH3CH2CH2CH2CH3 Hexane C6H14 CH3CH2CH2CH2CH2CH3 Heptane C7H16 CH3CH2CH2CH2CH2CH2CH3 Octane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3 Draw the structural formula Nonane C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3 Decane C10H22 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 Isomerism: Isomerism is a very common phenomenon in organic chemistry. Compounds that have the same molecular but different structural formulas are called isomers. Isomers start to happen from butane which has only two isomers. Number of isomers increase rapidly with the number of carbon atoms in the chain, but there is no general formula for prediction. There are three pentanes, five hexanes, nine heptanes. By the time it reaches 30 carbon atoms in the chain the number of possible isomers are over 4 billion. Physical and chemical properties of alkanes: The following Table shows some of the physical properties alkanes. They are nonpolar compounds, do not dissolve in water. Light alkanes such as those in gasoline (hexane, heptane, octane) dissolve and wash away body oils when spilled on the skin. Heavier alkanes, when applied on skin, act as emollients (petroleum jelly). Cyclic hydrocarbons: (Ring compounds: cycloalkanes, cycloalkenes, cycloalkynes) Cycloalkanes have a general formula of CnH2n, all carbon being in a closed chain. The simplest member is cyclopropane. Name Structure Name Structure Cyclopropane or Cyclobutane or Cyclopentane Cyclohexane Unsaturated hydrocarbons: (Alkenes - double bond, and alkynes - triple bond) Alkenes contain at least one carbon-to-carbon double bond (C=C) in the structure. The simplest member is ethylene, CH2=CH2. Its IUPAC name is ethene. Alkynes contain at least one carbon-to-carbon triple bond (C≡C). The simplest member is acetylene or ethyne. Unsaturated hydrocarbons undergo addition reaction. They also form polymers. Aromatic hydrocarbons: (Benzene, C6H6, and its relatives) Benzene, has been known to scientists with its molecular formula of C 6H6, which contains a lot of unsaturation. But these unsaturations do not act as those in an open chain unsaturated hydrocarbon. Kekulé proposed the ring structure with three alternating double bonds. Halogenated hydrocarbons: (Remember DDT and PCB? Not such a good friend to the environment.) One or more hydrogen atoms of a hydrocarbon can be substituted by halogens. Alkyl groups: Alkanes without one hydrogen. (Remember the stem names?) Functional groups: (family traits) Alcohols: (R–OH, only one is drinkable) When a hydroxyl group (–OH) is substituted for any hydrogen in an alkane, the molecule becomes an alcohol (R–OH). Methanol (CH3–OH), ethanol (CH3CH2–OH), propanol (CH3CH2CH2–OH), butanol (CH3CH2CH2CH2–OH) are some earlier members of the series. In the non-IUPAC system these names are called methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol. Other names and usage of alcohols: Multifunctional alcohols - ethylene glycol, glycerol Phenols: (Not an alcohol. OH is connected to a benzene ring.) Usage of phenols: Ethers: (Oxygen between two carbons, R–O–R or R–O–R') CH3–O–CH3 CH3CH2–O–CH2CH3 CH3–O–CH2CH3 CH3CH2–O–CH2CH2CH3 Usage of ethers: Aldehydes and ketones: (Formalin and nail polish remover. Carbonyl group is an important part.) Difference and similarities between aldehydes and ketones - R–CHO and R–CO–R' Usage of aldehydes and ketones: Carboxylic acids: (R–COOH, ever tasted vinegar?) Usage of carboxylic acids: Esters: (RCOOR', good smelling compounds) CH3COOCH2CH3 Apricot smell CH3CH2CH2COOCH2CH2CH2CH2CH3 Usage of esters: Nitrogen containing organic compounds: Amines: Organic derivatives of ammonia, NH 3. R–NH2, RR'–NH, RR'R"–N. Primary amines: CH3CH2–NH2 Secondary amines: Tertiary amines: CH3CH2CH2NH2 Aromatic amine: Summery table Compound type Formula IUPAC name Common name Alkane CH3-CH3 ethane ethane Alkene CH2=CH2 ethene ethylene ethyne acetylene Alkyne Alcohol CH3CH2OH ethanol ethyl alcohol Aldehyde CH3COH ethanal acetaldehyde Ketone propanone acetone Carboxylic acid ethanoic acid acetic acid ethylamine ethyl amine methyl ethanoate methyl acetate dimethyl ether dimethyl ether Amine CH3CH2-NH2 Ester Ether CH3-O-CH3 Aromatic hydrocarbon benzene benzene Aromatic acid benzoic acid benzoic acid | Home | | CHM151 | | Course Policy | | Office Hours | | WebCT Quiz | | Lab Write-up | | Useful Websites | | Your Instructor |