Types of Organic Compounds

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Rosa Wilkinson
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1 ORGANI EMISTRY Types of Organic ompounds Vast majority of over 0 million known compounds are based on : organic compounds. Generally contain and + other elements Great variety of compounds Isomerism Isomers have identical composition but different structures Two forms of isomerism onstitutional (or structural) Stereoisomerism onstitutional Same empirical formula but different atom- to-atom connections Stereoisomerism Same atom-to-atom connections but different arrangement in space. 5 6 Structural Isomers Stereoisomers: : Geometric Geometric isomers can occur when there is a = double bond. Stereoisomers: : Optical Optical isomers are molecules with non-superimposable mirror images. is-- --butene Trans--butene Such molecules are called IRAL Pairs of chiral molecules are enantiomers. hiral molecules in solution can rotate the plane of plane polarized light.

2 hiral ompounds and Polarized Light 7 Stereoisomers Isomers hirality generally occurs when a atom has different groups attached. 8 Stereoisomers Isomers 9 Lactic acid Lactic acid isomers are nonsuperimposable hirality: : andedness in Nature 0 hirality: : andedness in Nature Stereoisomers in Nature These molecules are non-superimposable mirror images. These amino acids are non- superimposable mirror images. Right- and left- handed seashells The DNA here is right-handed

3 5 ydrocarbons ydrocarbons ompounds of and Subgroups: Alkanes: : - single bonds Alkenes: : = double bonds Alkynes: : carbon-carbon triple bonds Aromatic: based on benzene Alkanes have the general formula n n+ = methane 6 = ethane 8 = propane 0 = butane 5 = pentane Methane ydrate, ( O) x 6 Methane ydrate, ( O) x 7 Methane ydrate, ( O) x Gas hydrates have been known for many years, and combustion of a sample of methane hydrate is seen on the front cover. Recently, however, vast deposits of methane hydrate were discovered deep within sediments on the floor of the world s oceans. ow these deposits were formed is a mystery. But what is important is their size. It is estimated that the global methane hydrate deposits contain approximately 0 tons of carbon, or about twice the combined amount in all reserves of coal, oil, and conventional natural gas. Now if scientists and engineers could only solve the problem of extracting the methane conveniently and safely! 8

4 Pentane -Methylbutane,-Dimethylpropane Note names of isomers ydrocarbons & Structural Isomerism Isomers of 5? 9 5 has structural isomers. 6 has 5 7 has 9 ydrocarbons: Alkanes Alkanes are colorless gases, liquids, and solids Generally unreactive (but undergo combustion) Not polar (or low polarity) and so are not soluble in water. 0 ydrocarbons: ycloalkanes All compounds are flexible. yclohexane,, 6, has interconverting chair and boat forms. Axial atom 6 5 hair form Equatorial atom 5 6 Boat form 5 6 hair form Alkenes: : ompounds with = Double Bonds ow many isomers are possible for a compound with the formula 8? -butene -methylpropene (isobutene) cis--butene trans--butene Alkenes Many Occur Naturally Reactions of Alkenes: ADDITION REATIONS are unsaturated more Alkenes are more bonds can form to the atoms Molecules such as Br,, l, Br,, and O add to the double bond Br Br + Br,-dibromoethane

5 An Addition Reaction 5 An Addition Reaction 6 An Addition Reaction 7 Fat placed in Br vapor Fat placed in Br vapor Fats can be hydrogenated with. The fat in bacon is partially unsaturated. The fat adds Br to the = bonds. Fats can be hydrogenated with. Peanut butter has partially hydrogenated vegetable oil. Alkynes Alkynes have carbon-carbon triple bonds. : common name = acetylene systematic name = ethyne Preparation: a (s) + O(liq) liq) ) --> (g) + a(o) (s) o fo (, g) = +6.7 kj/mol rxn for + O = 00 kj/mol 8 Aromatic ompounds Benzene, 6 6, in the top 5 chemicals produced in the U.S. Starting point for hundreds of other compounds. 9 Resonance in Benzene 6 6 has two resonance structures with alternating double bonds. The 0 electrons are delocalized over the ring. Resonance structures of benzene, 6 6 Abbreviated representation of resonance structures 5

6 Resonance in Benzene Other Aromatic ydrocarbons Benzene Derivatives bond order is single bond = 5 pm = bond = pm bonds in benzene = 9 pm electrons delocalized Toluene Naphthalene Aniline 6 5 N Phenol 6 5 O TNT trinitrotoluene 6 (NO ) Naming Benzene Derivatives 6 5 l Ortho to l Meta to l Para to l,-dimethylbenzene ommon name: Para-xylene Reactions of Aromatics Substitutions not additions are typical. + l All All is a catalyst. atalysts typically used in aromatic substitutions. 5 + l 6

ORGANIC COMPOUNDS IN THREE DIMENSIONS

ORGANIC COMPOUNDS IN THREE DIMENSIONS (adapted from Blackburn et al., Laboratory Manual to Accompany World of hemistry, 2 nd ed., (1996) Saunders ollege Publishing: Fort Worth) Purpose: To become familiar with organic molecules in three dimensions