Question

(b) Draw an example of each of the following: (i) 5-exo-tet (ii) 5-exo-trig (iii) 5-endo-dig reactions, In each case show a separate diagram of the starting structure, the transition state structure, and the product(s) structure.

Answer 1

(i). 5-exo-tet Here, 5 signifies the size of the cyclic ring that forms has 5 atoms in the ring.. The word exo signifies that the bond that breaks lies outside the cyclic ring that forms. The word tet signifies that the electrophilic atom center is tetrahedral or sp3 hybridised. Hence, an example of 5-exo-tet type reaction is -- NH ----Br 5 Br 1 2 4 transition state 5 membered ring starting structure Electrophile is the carbon with Br which is sp3 hybridised. Br-leaves Note that the C-Br bond which breaks lies outside the ring. * H Product

(ii). 5-exo-trig Here, 5 signifies the size of the cyclic ring that forms has 5 atoms in the ring. The word exo signifies that the bond that breaks lies outside the cyclic ring that forms. The word trigsignifies that the electrophilic atom center is trigonal or sp2 hybridised. Hence, an example of 5-exo-trig type reaction is 3 4 OH --ОН 2 10H 2 transition state 5 membered ring starting structure Electrophile is the carbon with double bonded O C-O bond breaks Note that the C-O bond which breaks lies outside the ring. Also note that the carbon with double bonded O and OH group is trigonal planar and sp2 hybridised. -ОН O OH Product

(iii). 5-endo-dig Here, 5 signifies the size of the cyclic ring that forms has 5 atoms in the ring.. The word endo signifies that the bond that breaks lies inside the cyclic ring that forms. The word dig signifies that the electrophilic atom center is diagonal or sp hybridised. Hence, an example of 5-endo-dig type reaction is 5 0 3 4 transition state 5 membered ring starting structure Electrophile is the carbon with triple bond bonded another C. Note that the Catom being attacked is sp hybridised as it has a triple bond. C-C bond breaks Product