Chemical Reactions of Unsaturated Compounds

Transcription

1 hemical Reactions of Unsaturated ompounds

2 hemical Reactions of Alkenes

3 hemical Reactions of Alkenes Structure of the Double Bond in Alkenes The two components of the double bond are pictured the same, but one of the bonds (the π bond) is actually weaker than the other.

4 hemical Reactions of Alkenes The characteristic reaction of alkenes is an ADDITION REATION. + A B "catalyst" A B A and B are not necessarily single atoms. A and B are added to the structural and molecular formula. WAT ARE A AND B? - X-X -X -O ydrogenation alogenation ydrohalogenation ydration

5 hemical Reactions of Alkenes A B A B "catalyst" A B A B

6 atalytic ydrogenation Ni or Pt catalyst Specific Examples 24 2, Ni or Pt catalyst 26 ethene ethane , Ni or Pt catalyst ,3-dimethyl-2-pentene 2,3-dimethylpentane

7 alogenation General Reaction Dark, no catalyst X X X X Specific Examples 24 ethene l 2, no catalyst l l 1,2-dichloroethane 24l l 2, no catalyst l l l2 2-methyl-2-pentene 2,3-dichloro-2-methylpentane

8 Addition of Bromine (Br2) Br 2 no catalyst Br Br Br Br Br 2 no catalyst Br 2 no catalyst No reaction

9 hemical Reactions of Alkenes Addition of Bromine (Br2) The result can be quantitated.

10 hemical Reactions of Alkenes Addition of Bromine (Br2) Alkane Br2 Alkene Alkane + Br2 Alkene + Br2

11 ydrohalogenation X + X or X Specific Example: l butene 48 l 3 3 or 2-chlorobutane l 49l chlorobutane In some cases only one product can be formed.

12 What is the result if two isomeric products are possible?? l l 3 2 l propene 3 2 l 1-chloropropane or ( ) l? ( ) chloropropane 37l

13 MARKOVINIKOV S RULE- When adding -X or -O (2O) to alkenes with different number of groups attached to the double bonds, the portion of the reagent adds to the carbon that has the greater number of hydrogen atoms already attached. -l -Br -O l l 3 2 l chloropropane propene l or l chloropropane Major product

14 ydration of Alkenes O + O or alkenes O alcohols O O or 3 3 2,3-dimethyl-2-butene O ,3-dimethyl-2-butanol 614O In some cases Maokovnikov s rule is not needed.

15 O ydration of Alkenes 3 3 O + O or methyl-2-butanol O * O O 2-methyl-2-butene * methyl-2-butanol 512O Major product

16 Alkynes The triple bond consists of two π components and one σ component. The characteristic reaction is addition to both of the π bonds. 2 mol of A-B A B A B

17 Alkynes Markovnikov s rule may or may not apply. Br Br 2 mol Br2 no catalyst Br Br l 2 mol l no catalyst 3 3 l

18 Alkene and Alkyne Reactions Worksheet

19 3 a) 2 Pt 510 b) 3 Br 2 dark 712Br2

20 3 c) 3 l 49l d) 2 O + 510O 58

21 e) 2 O O f) 3 Br 713Br

22 1a) l Excess Br 2 in the dark l 2,2-dichloro-5-methyl-3-hexyne 710Br4l2 1b) Excess Br in the dark 3 816Br2 5,5-dimethyl-1-hexyne

23 Addition Polymers Overall Reaction: A X A X A X A X A X = = = = = B Y B Y B Y B Y B Y Acid or initiator A X A X A X A X A X B Y B Y B Y B Y B Y A X ( ) n n = number of individual units B Y

24 Addition Polymers Monomer Polymer Uses 2 2 (2 2 )n bottles, toys, housewares, wire cable insulation, plastic sheeting ethylene polyethylene 2 (2 )n outdoor carpeting, food packaging appliance housings 3 3 propylene polypropylene 2 (2 )n styrofoam containers, food packaging hairbrush handles, toys styrene polystyrene

25 Addition Polymers Monomer Polymer Uses 2 ( 2 ) n home siding, gutters, flooring, garden hose, PV tubing l l vinyl chloride polyvinylchloride (PV) 2 ( 2 ) n acrylic textile fibers N N acrylonitrile polyacylonitrile F2 F2 tetrafluoroethylene (F2 F2 )n polytetrafluoroethylene Teflon, mechanical parts, cookware, chemical resistant gaskets

26 Aromatic ydrocarbons

27 Aromatic ydrocarbons Benzene (66) was discovered in 1825, but a partially correct structure was not proposed until 1865 by August Kekule. The structure consisted of six carbons in a ring joined by alternating single and double bonds. Physical and chemical evidence indicates that benzene behaves as if all the carbon-carbon bonds are identical. ence, the following structural representation is sometimes used:

28 Great Events in hemistry 1865:Kekule, moments before his brilliant insight into the structure of benzene.

29 Uroboros

30 Resonance in Benzene

31 Delocalized Bonding in Benzene sigma bonding system sp2 hybrid orbitals remaining p orbitals delocalized pi bonding

32 Aromatic ydrocarbons-nomenclature 1. Identify the benzene ring in a compound and assign the parent name benzene 2. Attach names and location of substituents. 3. For two or more substituents, number the benzene ring starting with one of the substituents to give the lowest combination of numbers to the substituents. 4. Some important monosubstituted benzenes have common names: O O O 3 O N 2 Toluene Phenol Aniline Benzoic Acid Benzaldehyde

33 Aromatic ydrocarbons-nomenclature 5. The prefixes ortho (o), meta (m), and para (p) are often used to indicate the relative positions of two substituents in 1,2-, 1,3-, and 1,4- placement on a benzene ring. Br O N 2 Br NO 2 1,2-dibromobenzene 1-hydroxy-3-nitrobenzene 1-amino-4-chlorobenzene ortho-dibromobenzene meta-nitrophenol para-chloroaniline l

34 Aromatic ydrocarbons-nomenclature

35 Worksheet on Aromatic ompounds

36 1. Describe the relationship between the following pairs of compounds: a) b) c) Br Br Br l and and and l l l l l Br Br Br

37 2. Name the following compounds as substituted benzenes. a) b) c) l 2 3 l NO 2 3 Br N 2

38 3. Name the following compounds using the base name which is given a) b) c) O O O Br O l phenol benzoic acid phenol Br

39 Aromatic ydrocarbons-nomenclature 4. The benzene ring may be named as a subsituent. 3 3 l 2 3

40 The Benzene Ring in Drug Molecules O O 3 O 3 O 3 O O 2 3 Aspirin Ibuprofen O 3 3 innamedrine Dextromethorphan

41 Aromatic ydrocarbons Substitution Reactions l l O 3 S O? l O O 2 N O O

42 Aromatic ydrocarbons Substitution Reactions l l 2 Fe 66 65l SO3 2 SO 4 heat 66 65SO3

43 Aromatic ydrocarbons Substitution Reactions NO2 NO 3 heat 66 65NO2 3 3 O2N NO2 NO3 heat NO3 heat NO3 heat Tri Nitro Toluene NO2