Organic Chemistry, 5th Edition H H L.G. Wade Jr Chapter 9 Alkynes Jo blackburn Richland college, dallas TX Dallas County Community College District c 2003. Prentice hall
Chapter 9 Alkynes Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
H H Introduction Alkynes contain a triple bond General formula is CnH2n-2 Two elements of unsaturation for each triple bond Some reactions are like alkenes addition and oxidation Some reactions are specific to alkynes > Chapter 9
Chapter 9 2 Introduction • Alkynes contain a triple bond. • General formula is CnH2n-2 • Two elements of unsaturation for each triple bond. • Some reactions are like alkenes: addition and oxidation. • Some reactions are specific to alkynes. =>
Nomenclature: UPAC H Find the longest chain containing the riple bond Change -ane ending to yne Number the chain, starting at the end closest to the triple bond Give branches or other substituents a number to locate their position = Chapter 9
Chapter 9 3 Nomenclature: IUPAC • 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 substituents a number to locate their position. =>
H H Name these CHC≡CH propyne CH-C≡C-CH2CH2-Br 5-bromo-2-pentyne CHCH-CH2C≡C-CH-CH3 2, 6-dime thyl-3-he pyne => Chapter 9
Chapter 9 4 Name these: CH3 CH CH3 CH2 C C CH CH3 CH3 CH3 C C CH2 CH2 Br CH3 C CH propyne 5-bromo-2-pentyne 2,6-dimethyl-3-heptyne =>
Additional functional H Groups All other functional groups, except ethers and halides have a higher priority than alkynes For a complete list of naming priorities look inside the back cover of your ter > Chapter 9
Chapter 9 5 Additional Functional Groups • All other functional groups, except ethers and halides have a higher priority than alkynes. • For a complete list of naming priorities, look inside the back cover of your text. =>
H H Examples CH CH2=CHCH2-CH-C≡CH 4-methyl-l-hexen-5-yne CH3C≡C-CH2-CH-CH 4-hexyn-2-ol > Chapter 9
Chapter 9 6 Examples CH2 CH CH2 CH CH3 C CH 4-methyl-1-hexen-5-yne CH3 C C CH2 CH OH CH3 4-hexyn-2-ol =>
H H Common names Named as substituted acetylene CH3C=CH methylacetylene CH3 CH CH3CH-CH2C≡CCH-CH isobutylisopropylacetylene Chapter 9
Chapter 9 7 Common Names Named as substituted acetylene. CH3 C CH methylacetylene CH3 CH CH3 CH2 C C CH CH3 CH3 isobutylisopropylacetylene =>
H H Physical Properties Nonpolar, insoluble in water Soluble in most organic solvents Boiling points similar to alkane of same SIze Less dense than water Up to 4 carbons, gas at room temperature > Chapter 9
Chapter 9 8 Physical Properties • Nonpolar, insoluble in water. • Soluble in most organic solvents. • Boiling points similar to alkane of same size. • Less dense than water. • Up to 4 carbons, gas at room temperature. =>
H H Acetylene Acetylene is used in welding torches In pure oxygen, temperature of flame reaches2800° It would violently decompose to its elements, but the cylinder on the torch contains crushed firebrick wet with acetone to moderate it > Chapter 9
Chapter 9 9 Acetylene • Acetylene is used in welding torches. • In pure oxygen, temperature of flame reaches 2800C. • It would violently decompose to its elements, but the cylinder on the torch contains crushed firebrick wet with acetone to moderate it. =>
H H Synthesis of Acetylene Heat coke with lime in an electric furnace to form calcium carbide Then drip water on the calcium carbide 3c+ Cao y Cac2 co coke lime Ca C2+ 2 Ho H-C≡C-H+Ca(OH2 *This reaction was used to produce light for miners' lamps and for the stage > Chapter 9 10
Chapter 9 10 Synthesis of Acetylene • Heat coke with lime in an electric furnace to form calcium carbide. • Then drip water on the calcium carbide. CaC2 + 2 H2O H C C H + Ca(OH) 2 3 C + CaO CaC2 + CO coke lime *This reaction was used to produce light for miners’ lamps and for the stage. => *