Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Naming Alkenes and Alkynes STEP 1: Name the main chain. Find the longest continuous chain of carbons containing the double or triple bond. The names of alkenes end with –ene, and the names of alkynes end with -yne. When there is more than one multiple bond, use numerical prefixes (diene, diyne, triene, triyne, etc.) CH 3 CH 2 CH 2 CH CH 3 CH 2 CH 2 CH 3 CH 2 C CH 3 CH 2 CH CH 2 C C CH 3 Name as hexyne - a six C chain containing a double bond Name as p entene - a f ive C chain containing a double bond CH 3 CH 2 CH 2 CH 2 C CH3 CH 3 CH 2 CH 2 CH CH3 CH 2 not as a heptene - the double bond is not contained on the seve C chain. Name as hexene - a six C chain containing a double bond... STEP 2: Number the carbon atoms in the main chain. Begin at the end nearer the multiple bond. If the multiple bond is at the same distance from both ends, begin numbering at the end nearer the first branch point. CH 3 CH 3 CH3 CH 2 CH 2 CH CH CH 3 4 6 5 3 2 1 This end is closer to the double bond. CH 3 C C CH2 CH 2 CH 2 CH CH 3 CH 3 CH CH CH CH 2 CH 3 1 2 3 4 5 6 2 6 7 8 1 4 5 3 Both ends are at the same distance The lef t end is closer to the triple bond. f rom the double bond, but this is closer to the branch. The double-bond carbon atoms in substituted cycloalkenes are numbered 1 and 2 so as to give the first substituent the 3 lowest number: Do not begin here. CH3 2 4 1 6 1 5 6 If we start here the brach gets the lowest possible number CH3 5 2 4 3 STEP 3: Write the full name. Assign numbers to the branching substituents, and list the substituents alphabetically. Indicate the position of the multiple bond(s) in the chain by giving the number of the first multiple-bonded carbon. If more than one multiple bond is present, identify the position of each multiple bond and use the appropriate ending diene, triene, tetraene, and so forth. 6 CH3 CH3 5 CH2 4 CH2 CH 3 2 1-pentene or pent-1-ene CH2 CH3 6 1 CH2 5 CH 3 CH3 C 1 2 Reyes C 3 CH2 CH2 CH 2 4 5 6 CH 7 7-methyl-2-octyne or 7-methyloct-2-yne CH2 C 4 3 2-hexyne or hex-2-yne C 2 CH 2 1 C 2 CH 3 CH2 CH2 CH3 1 3 C CH3 CH2 2 CH 1 CH 3 CH2 3-propyl-2-hexene or 3-propylhex-2-ene CH 2 CH 3 CH 3 8 4 5 3 CH2 4 2-ethyl-1,3-butadiene or 2-ethylbuta-1,3-diene 2 CH 3 4 1 5 6 4-methylcyclohexene Assigning Priority What happens when double and triple bonds appear in the same molecule? • • • • Alkenes and alkynes are considered to have equal priority. In a molecule with both a double and a triple bond, whichever is closer to the end of the chain determines the direction of numbering. In the case where each would have the same position number, the double bond takes the lower number. In the name, “ene” comes before “yne” because of alphabetization. 1 2 3 4 5 CH C CH CH CH 3 pent-3-en-1-yne ("yne" closer to end of chain) 10 8 9 7 5 4 3 2 1 CH C CH 2 CH CH 2 pent-1-en-4-yne ("ene" goes f irst in the alphabet and takes priority over "yne") 6 4 5 2 3 1 deca-5,7-dien-1,3-diyne • Reyes Notice how in the names the last letter of the “—ene” ending is dropped to let people know that the molecule has more functional groups (triple bonds in the examples above).