Question

Estimate the stabilization energy for 1,3-pentadiene using the heats of hydrogenation in Table 1. Table 1. Heats of Hydrogenation for Selected Compounds Compound Moles H2 A H(kJ mol-?) 1-Butene 1 - 127 1-Pentene 1 -126 trans-2-pentene 1 -115 1,3-Butadiene 2 -239 trans-1,3-Pentadiene 2 -226 X 112 kJ mol-1 O 13 k) mol-1 239 kJ mol-1 15 kJ mol-1 28 kJ mol-1

Answer 1

1. Stabilization energy

Each compound has a theoritical and an experimental value of heat of hydrogenation.

Here, theoritical value of 1,3-pentadiene can be calculated using the heat of hydrogenation of 1-pentene and trans-2-pentene.

From the table, we have the theoritical value of heat of hydrogenation of 1,3-pentadiene =

-(126+115)kJ/mol. = -241kJ/mol

And , the experimetal value was given is -226 kJ/mol

Hence, the stabilization energy will be =

| difference between theoritical and experimental values| kJ/mol

= 15kJ/mol.(Ans.)

2. The diene of Diels Alder reaction will be

only str. (IV)