1. John E. McMurry www.cengage.com/chemistry/mcmurry Paul D. Adams University of Arkansas Chapter 10 Organohalides

2.  An organic compound containing at least one carbon-halogen bond (C-X)  X (F, Cl, Br, I) replaces H  Can contain many C-X bonds  Properties and some uses  Fire-resistant solvents  Refrigerants  Pharmaceuticals and precursors What Is an Organohalide?

3.  Reactions involving organohalides are less frequently encountered than other organic compounds, but reactions such as nucleophilic substitutions/eliminations that they undergo will be encountered  Alkyl halide chemistry is model for mechanistically similar but more complex reactions Why this Chapter?

4.  Find longest chain, name it as parent chain  (Contains double or triple bond if present)  Number from end nearest any substituent (alkyl or halogen) 10.1 Naming Alkyl Halides

5.  Begin at the end nearer the substituent having its name first in the alphabet Naming if Two Halides or Alkyl Are Equally Distant from Ends of Chain

6. 1) Naming Alkyl Halides http://www.khanacademy.org/science/orga nic-chemistry/v/naming-alkyl-halides Naming Alkyl Halides - Video

7.  C-X bond is longer as you go down periodic table  C-X bond is weaker as you go down periodic table  C-X bond is polarized with slight positive charge on carbon and slight negative charge on halogen Structure of Alkyl Halides

8.  Alkyl halide from addition of HCl, HBr, HI to alkenes to give Markovnikov product (see Alkenes chapter)  Alkyl dihalide from anti addition of bromine or chlorine 10.2 Preparing Alkyl Halides from Alkenes: Radical Halogenation

9.  Alkane + Cl 2 or Br 2, heat or light replaces C-H with C-X but gives mixtures  Hard to control  Via free radical mechanism  It is usually not a good idea to plan a synthesis that uses this method Preparing Alkyl Halides from Alkenes: Radical Halogenation

10.  If there is more than one type of hydrogen in an alkane, reactions favor replacing the hydrogen at the most highly substituted carbons (not absolute) Radical Halogenation of Alkanes

11.  Based on quantitative analysis of reaction products, relative reactivity is estimated  Order parallels stability of radicals  Reaction distinction is more selective with bromine than chlorine Relative Reactivity

12. 1) Free Radical Halogenation of Alkane http://www.youtube.com/watch?v=5HgzsltWwK 8&feature=player_embedded Radical Halogenation of Alkanes - Video

13.  N-bromosuccinimide (NBS) selectively brominates allylic positions  Requires light for activation  A source of dilute bromine atoms 10.3 Preparing Alkyl Halides from Alkenes: Allylic Bromination

14.  Allyl radical is delocalized  More stable than typical alkyl radical by 40 kJ/mol (9 kcal/mol)  Allylic radical is more stable than tertiary alkyl radical Allylic Stabilization

15. 1) Allylic bromination of alkenes http://www.youtube.com/watch?v=q- zwxLxy6Ew&feature=player_detailpage Allylic Bromination - Video

16.  Three electrons are delocalized over three carbons  Spin density surface shows single electron is dispersed 10.4 Stability of the Allyl Radical: Resonance Revisited

17.  Allylic bromination with NBS creates an allylic bromide  Reaction of an allylic bromide with base produces a conjugated diene, useful in the synthesis of complex molecules Use of Allylic Bromination

18.  Reaction of tertiary C-OH with HX is fast and effective  Add HCl or HBr gas into ether solution of tertiary alcohol  Primary and secondary alcohols react very slowly and often rearrange, so alternative methods are used 10.5 Preparing Alkyl Halides from Alcohols

19. 1) Conversion of Alcohols to Alkyl Halides http://www.youtube.com/watch?v=tJx8yRyCa9 M&feature=player_detailpage Preparing Alkyl Halides from Alcohols - Video

20.  Reaction of RX with Mg in ether or THF  Product is RMgX – an organometallic compound (alkyl-metal bond)  R is alkyl 1°, 2°, 3°, aryl, alkenyl  X = Cl, Br, I 10.6 Reactions of Alkyl Halides: Grignard Reagents

21. 1) Reactions of Alkyl Halides: Grignard Reagents http://www.youtube.com/watch?v=5sVQdn kJsGI&feature=player_detailpage&list=LP0 HDqUK2QPyk Reactions of Alkyl Halides: Grignard Reagents - Video

22.  Alkyllithium (RLi) forms from RBr and Li metal  RLi reacts with copper iodide to give lithium dialkylcopper (Gilman reagents)  Lithium dialkylcopper reagents react with alkyl halides to give alkanes 10.7 Organometallic Coupling Reactions

23.  Coupling of two organometallic molecules produces larger molecules of defined structure  Aryl and vinyl organometallics also effective  Coupling of lithium dialkylcopper molecules proceeds through trialkylcopper intermediate Utility of Organometallic Coupling in Synthesis

24. 1) Organolithium Reagents - Start 21:34, Finish 23:10 http://www.youtube.com/watch?v=ZLa6AsmXp50&feature= player_detailpage 2) Gilman Reagent and Suzuki Reaction. START 23:55, END 25:35 http://www.youtube.com/watch?v=Aku- z1IbF98&feature=player_detailpage 3) The Suzuki-Miyaura reaction http://www.youtube.com/watch?v=7CpwtOGjDPs&feature=p layer_detailpage Organometallic Coupling Reactions - Video

25.  In organic chemistry, we say that oxidation occurs when a carbon or hydrogen that is connected to a carbon atom in a structure is replaced by oxygen, nitrogen, or halogen  Not defined as loss of electrons by an atom as in inorganic chemistry  Oxidation is a reaction that results in loss of electron density at carbon (as more electronegative atoms replace hydrogen or carbon)  Oxidation: break C–H (or (C–C) and form C–O, C–N, C–X 10.8 Oxidation and Reduction in Organic Chemistry

26.  Organic reduction is the opposite of oxidation  Results in gain of electron density at carbon (replacement of electronegative atoms by hydrogen or carbon)  Reduction: form C–H (or C–C) and break C–O, C–N, C–X Reduction Reactions

27.  Functional groups are associated with specific levels Oxidation Levels

28. How would you carry out the following syntheses? Let’s Work a Problem

29. Answer The dialkylcopper reagent should be used (di- butylCuLi) that can be added to cyclohexylBr after cyclohexene is treated with HBr.