Question

hange of hydrogenation of an unsaturated hydrocarbon is the enthalpy change mole of the compound reacts completely with hydrogen to form a saturated Delocalised t system and resonance energy 7 (a) The enthalpy change of hydrogenation of an when one mole of the com hydrocarbon. The enthalpy chang arbon. The enthalpy change of hydrogenation of cyclohexene, CHI), is - 120 kJ mol. Write an equation of the reaction that represents the enthalpy change of hydrogenation of cyclohexene. (b) ophthalene, C10Hg(s), is an example of an aromatic hydrocarbon like benzene. When naphthalene is fully hydrogenated, decalin, C10H 18(S), is formed. The enthalpy change of hydrogenation of naphthalene is -345 kJ mol-1 O O (s) hydrogenaton, NY (s) naphthalene decalin The resonance energy of naphthalene can be defined as the energy difference between the actual structure of naphthalene (I) and the hypothetical structure of naphthalene (II).
Just answer part b & c

Answer 1

7 ch) formula used: Resonance = enthalpy of hydrogenation - enthalpy of hydrogenation energy CRE) of adual structure of hypothetical structure Equation: a + H₂ O Angd H - 120 kJ mol for each double bond, energy released is - 120 k3 moi O + 5 Hz - Dhyd = -120x5 book Imeil (hypothetical) there are 5 double bonds . energy released is - 5x6120) - 600kJ mol RE= - 345 -(-60o) = 255 KJ mot b(given -value) RE = 255kJ mot for actual structure .. A TRET T O Imaginary structure PE - 3957-ta-t o ro actual structure for actual strudur boo off mol) - 20 a cyclohenene (c) Approximate calculations, of Ametlef anthracene Type I: Using no. of rings : napthalene with two rings has RE of 255 kJ mot! Auto RE per ring - 255 = 127.5K3 mol n a anthracene has 3 rings & RE of anthracene = 127.5*3 = 382.5kImol

. Enthalpy of RE+ Centhalpy of hydroge. hydrogenation of is actual structure Aucure) 382.5 + [6-120x7 as there are = 1 - 457.5 kJ mol 7 double bonde (OR) (-108, 92 Kealmol) Type II : Using number of resonance structures napthalene with three 2 has RE of +255 KJ mol resonance structures y RE per structure = 255 = 85 ki mol in anthracene with four resonance structures, approximate Re = 85 x 4 = 340 KI mol i hydrogen Hof RE+ Shydrogenation of actual anthracone imaginary structure : 340+ ((- 120x17] : -500 kImol (-119.33 Keal mot) Exact value of hydrogenationt of = - 116.2 Kealmol actual anthracene from literature clource) . Type - I is a better approach