Which one of the following has the smallest heat of hydrogenation per mole? (1993)
TIPS/Formulae : Heat of hydrogenation is related to stability of molecules; higher the stability, lower is the heat of hydrogenation.
Butadiene, CH2 = CHCH = CH2 has two double bonds so its heat of hydrogenation will be more than the other three.
Alkenes follow the following order of stability
Thus here stability order of the given monoalkenes is
NOTE : The trans-2-butene is more stable than the cis-because in the cis-isomer the two bulky groups are crowded together with the result it has more van der Waal’s strain than the trans-isomer.
Toluene, when treated with Br2/Fe, gives p-bromotoluene as the major product because CH3 group (1999 - 3 Marks)
Hyperconjugation in toluene activates the benzene ring for electrophilic substitution.
N(isomeric products) ; C5H11Cl
(isomeric products) Identify N and M (2006 - 5M,)
Identify N and M (2006 - 5M, –1)
So, the value of N will be 1 + 2 + 2 + 1 = 6.
Since enantiomers have nearly same physical properties, II and III as well as IV and V can’t be separated, hence the number of isomers (M) will be 1 + 1 + 1 + 1 = 4.
Among P, Q, R and S, the aromatic compound(s) is/are (JEE Advanced 2013-I)
Note : P has 2 p electrons, while Q, R & S have 6 p electrons each. Hence all the 4 are aromatic.
In the following reaction, the major product is (JEE Adv. 2015)
Compound(s) that on hydrogenation produce(s) optically inactive compound(s) is (are) (JEE Adv. 2015)
Among th e followin g, r eaction(s) wh ich gives(give) tert-butyl benzene as the major product is(are) (JEE Adv. 2016)