The heat of hydrogenation for 1-pentene is –126 kJ/mol when reacting with one mole of H2. Calculate the heat of hydrogenation expected if two moles of H¬2 react with one mole of a pentadiene. The experimentally measured heat of hydrogenation for 1,2-pentadiene is – 296 kJ/mol, 1,3-pentadiene is – 226 kJ/mol and 1,4-pentadiene is – 254 kJ/mol. Explain the order of stability of conjugated, cumulated and isolated dienes using this information.
2007-02-25 16:18:49 · 1 answers · asked by afchica101 1 in Science & Mathematics ➔ Chemistry
If there were no external effects, one would expect the heat of hydrogenation for pentadiene to be around -252kJ/mole. The 1,4- isomer heat is close to this, so it is expected to be an isolated diene. The conjugated 1,3-diene is most stable, and the cumulated is least stable due to the immediate proximity of the double bonds on the same 2- carbon.
2007-02-25 16:32:02 · answer #1 · answered by cattbarf 7 · 0⤊ 0⤋