1. ALKYNES C n H 2n-2 Dr. Marwa Eid 1

2. Alkyne Alkynes contain a triple bond. General formula is C n H 2n-2 Two elements of un-saturation for each triple bond. Some reactions are like alkenes: addition and oxidation. Some reactions are specific to alkynes. 2

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4. Nomenclature Find the longest chain containing the triple bond. Change -ane ending to -yne. Number the chain, starting at the end closest to the triple bond. Give branches or other substituent a number to locate their position. 4

5. 5 propyne 5-bromo-2-pentyne

6. 6 methylacetylene isobutylisopropylacetylene

7. 7 4-methyl-1-hexen-5-yne

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9. 9 Acetylene, the simplest alkyne Acetylene is used in welding torches. (In pure oxygen, temperature of flame reaches 2800  C)

10. 10 Synthesis of Acetylene Heat coke with lime in an electric furnace to form calcium carbide. Then drip water on the calcium carbide: coke lime CCaO 3 + + CaC 2 CO HCCH Ca(OH) 2 CaC 2 +2 H 2 O + Calcium carbide Electric furnace

11. Synthesis of Acetylene Acetylene is produced industrially from methane and steam at high temperature 11

12. 12 Alkyne Addition Reactions : 1. Hydrogenation 2. Halogenation 3. Hydration

13. Hydrogenation Addition of Hydrogen in the presence of metal catalyst (Pd, Pt, or Ni) to reduce alkyne to alkane, completely saturated. 13

14. Hydrogenation Addition of Hydrogen in the presence of metal catalyst (Pd, Pt, or Ni) to reduce alkyne to alkane, completely saturated. 14

15. You can use a reduced activity catalyst (Lindlar), Pd and Pb, which stops at the alkene. You obtain a cis A Lindlar catalyst is a catalyst that consists of palladium deposited on calcium carbonate treated with various forms of lead. Hydrogenation

16. Addition of Halogens Cl 2 and Br 2 add to alkynes to form vinyl dihalides. Product is mixture of cis and trans isomers. Difficult to stop the reaction at dihalide. 16

17. 17 Addition of HX Addition of HCl, HBr, and HI add to alkynes to form vinyl halides.

18. Hydration Reaction of alkynes with water 18

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