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Chemistry Dr. May Notes – Organic Chemistry Introducing Carbon Compounds There are over 6,000,000 carbon compounds known. 300,000 new ones are synthesized each year. Dr. May has contributed over 1000 new compounds to this list. Where do carbon compounds come from? Plant material fell to the forest floor and pressure and heat turned it into coal. Destructive (anaerobic) distillation can turn coal into a variety of organic compounds. Small plant organisms settled into prehistoric ooz, formed methane gas, modified itself and formed petroleum and natural gas. Living organisms synthesize a variety of Organic Chemicals. These include: proteins, sugars, cellulose, starches, vitamins, oils, waxes, and fats. Sorting out organic compounds The properties of a compound depend on both the composition and the structure. This gives us a variety of different compounds from the same composition depending on the structure forming a different isomer. A hydrogen in a hydrocarbon can be replaced with a different nonmetal element to form a derivative. Carbon can bond with itself (covalent bond using the four valence electrons) to form a carbon backbone. This carbon backbone can be a straight chain (unbranched) or branched. Carbon can be connected to itself by a single bond (saturated) or by a double bond or triple bond (unsaturated). The structure of many hydrocarbons are condensed when two or more groups occur together as in n-octane below: CH3CH2CH2CH2CH2CH2CH2CH3 = CH3(CH2)6CH3 Alkanes Alkanes are saturated hydrocarbons. That means that they have all the hydrogens they can hold and there are no double or triple bonds. 1 Naming hydrocarbons Alkanes are named according to the longest string of carbons as shown below for straight-chain (unbranched) hydrocarbons. Chemical Formula Longest Carbon Chain CH4 CH3CH3 CH3CH2CH3 CH3(CH2)2CH3 CH3(CH2)3CH3 CH3(CH2)4CH3 CH3(CH2)5CH3 CH3(CH2)6CH3 CH3(CH2)7CH3 CH3(CH2)8CH3 1 2 3 4 5 6 7 8 9 10 Name Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane Alkenes Alkenes have one or more double bond between two or more of the carbons. The carbons are sharing two pairs of electrons. Alkenes are unsaturated meaning that they can hold more hydrogens or that all the carbons do not have as much hydrogen around it as it could have. If hydrogen gas (plus a catalyst) is shaken up with an alkene, it will become an alkane. Alkenes are named like alkanes, but we need to tell where the double bond is by designating the number of the carbon where it is located. For example the structure below is 1 2 3 4 5 6 CH3CH2CH=CHCH2CH3 3-hexene CH3CH=CHCH2CH2CH3 2-hexene CH2=CHCH2CH2CH2CH3 6 5 4 3 2 1 CH3CH2CH2CH2CH=CH2 1-hexene 1-hexene The same but numbered the opposite direction to make the smaller # (not 5-hexene) Alkynes Alkynes have a triple bond. Two or more of the carbons are sharing three pairs of electrons. Like the alkenes, the position of the triple bond needs to be designated by giving the number of the carbon that the triple bond is associated with. 2 Aromatic hydrocarbons Benzene is the classic aromatic compound. It is composed of six carbons in a hexane ring. Each carbon has one hydrogen attached to it. The bonds between the carbons are half-single and half-double. The structure is half of the time (a), half the time (b), represented as (c), and sometimes simply as the Greek letter phi (). ⇄ ⇄ a b c Functional groups Group Name General Structure Example Example Name Alcohol (Hydroxyl) Ether (Alkoxy) Aldehyde (Carbonyl) ROH CH3CH2OH Ethanol ROR CH3CH2OCH2CH3 O ║ RCH O ║ RCR O ║ RCOH O ║ RCOR RNH2 RNR2 O ║ RCNH2 ROOR RCN RSR RSH RNO2 CH3CHO Diethyl ether (Ethoxy Ethane) Acetaldehyde (Ethanal) Ketone (Carbonyl) Acid (Carboxyl) Ester Amine Amide Peroxide Nitrile Sulfide Mercaptan Nitro 3 CH3COCH3 Acetone (Propanone) CH3COOH Acetic Acid (Ethanoic Acid) CH3COOCH2CH3 Ethyl Acetate CH3CH2NH2 Ethyl Amine CH3CONH2 Acetamide CH3OOCH3 NCCH2COOH CH3SCH3 CH3CH2SH CH3NO2 Dimethyl Peroxide Cyanoacetic acid Dimethyl Sulfide Ethyl Mercaptan Nitromethane Substitution and addition CH4 + methane Cl2 CH2=CH2 Ethene + O ║ CH3COH Acid H2O + O ║ CH3COH Acid CH3Cl + chloromethane CH3OH alcohol + CH3CH2OH ethanol O ║ CH3COCH3 ester CH3NH2 amine HCl O ║ CH3CNHCH3 amide + H2O + H2 O Oxidation and reduction [O] represents an oxidizing agent like copper oxide or potassium dichromate. CH3CH2OH Alcohol OH | CH3CHCH3 Isopropyl Alcohol + + [O] [O] O ║ CH3CH aldehyde O ║ CH3CCH3 + + H2O H2O acetone Polymerization CH2=CH2 Ethene or Ethylene O ║ NH2CH2COH + Amino acid glycine [CH2CH2]n polyethylene O ║ NH2CH2COH glycine O O ║ ║ [NHCH2CNHCH2C]n protein 4