General Chemistry II. Dr Rick Attrill. Office MHMK 1405/5. Classification of Hydrocarbons. Common Elements in Organic Compounds. Organic Chemistry I

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1 Organic hemistry I General hemistry II Dr Rick Attrill Office MMK 1405/5 lasses of Organic ompounds Aliphatic ydrocarbons Alkanes ycloalkanes Alkenes Alkynes Aromatic ydrocarbons 1 2 ommon Elements in Organic ompounds lassification of ydrocarbons ydrocarbons are made of only hydrogen and carbon. O, N, S, P, F, l, etc. are called heteroatoms. 4

2 Alkanes Alkanes have the general formula n 2n+2 where n = 1,2,, only single covalent bonds saturated hydrocarbons because they contain the maximum number of hydrogen atoms that can bond with the number of carbon atoms in the molecule methane ethane propane 5 Structural isomers are molecules that have the same molecular formula but different structures 6 Line Formula Line Formula 2 Dash formula Line formula ondensed formula 7 8

3 ow many structural isomers does pentane, 5 12, have? Draw them all using dash and line formula Alkane Nomenclature Alkane Nomenclature 1. The parent name of the hydrocarbon is that given to the longest continuous chain of carbon atoms in the molecule methylheptane 2. An alkane less one hydrogen atom is an alkyl group. 4 methane methyl 11 12

4 Alkane Nomenclature. When one or more hydrogen atoms are replaced by other groups, the name of the compound must indicate the locations of carbon atoms where replacements are made. Number in the direction that gives the smaller numbers for the locations of the branches methylpentane methylpentane 1 Alkane Nomenclature 4. Use prefixes di-, tri-, tetra-, when there is more than one alkyl branch of the same kind ,-dimethylhexane ,-dimethylhexane 14 Alkane Nomenclature What is the IUPA name of the following compound? 5. Use previous rules for other types of substituents NO bromo--nitrobutane What is the structure t of 2-propyl-4-methylhexane? lh NO bromo--nitrobutane 15 16

5 Alkane Reactions ombustion 4 (g) + 2O 2 (g) O 2 (g) O (l) 0 = kj alogenation light 4 (g) + l 2 (g) l (g) + l (g) Give two more possible propagation p reactions for: 4 (g) + l 2 (g) light l (g) + l (g) l 2 + energy l + l INITIATION 4 + l + l PROPAGATION + l Side reactions: l TERMINATION l + l l Optical isomers are compounds that are nonsuperimposable mirror images of each other Most simple chiral molecules contain at least one asymmetric carbon atom that is, a carbon atom bonded to four different atoms or groups of atoms Is the following molecule chiral? achiral chiral 19 20

6 Wedge and Dash Notation Use wedge and not notations to show the two optical isomers of the amino acid (N 2 )O 2 : in the plane points behind asymmetric carbon atom points in front sp - tetrahedral geometry ycloalkanes Alkanes whose carbon atoms are joined in rings are called cycloalkanes. They have the general formula n 2n where n =,4, Alkenes Alkenes have the general formula n 2n where n = 2,, contain at least one carbon-carbon double bond also called olefins butene 2-butene l l l l cis-dichloroethyleney trans-dichloroethyleney 2 geometric isomers 24

7 Alkene Reactions racking 2 6 (g) Pt catalyst 2 2 (g) + 2 (g) Addition Reactions 2 2 (g) + (g) 2 (g) 2 2 (g) + 2 (g) 2 2 (g) Alkynes Alkynes have the general formula n 2n-2 where n = 2,,4, contain at least one carbon-carbon triple bond 2 1-butyne Production of acetylene 2-butyne a 2 (s) O (l) 2 2 (g) + a(o) 2 (aq) Alkyne Reactions Aromatic ydrocarbons ydrogenation (g) + 2 (g) 2 2 (g) Addition Reactions (g) + (g) 2 (g) (g) + 2 (g) (g) (g) (g) 2 2 (g) 27 28

8 Aromatic ompound Nomenclature Aromatic ompound Reactions ethylbenzene aminobenzene Substitution reaction 2 l N 2 NO chlorobenzene nitrobenzene ,2-dibromobenzene 1,-dibromobenzene 29 Fe catalyst 2 All + 2 l + l catalyst 0 Polycyclic Aromatic ydrocarbons Line formula of Alkenes, Alkynes and Aromatics sp 2 - trigonal planar sp - linear sp 2 1 2