Radicals

Question 1

stability of carbon radicals

Answer 1

primary < secondary < tertiary < allyl = benzyl

Question 2

ketyl radical formation

Answer 2

ketone and Na

Question 3

ketyl radicals in protic solvent

Answer 3

forms alcohol

Question 4

ketyl radicals in hydrocarbon solvent with chelating metal

Answer 4

pinacole reaction, divalent chelating metal promotes C-C formation by holding radicals close, forms 1,2-diol

Question 5

McMurry reaction

Answer 5

TiCl3 with Zn/Cu or LiAlH4, Ti(III) reduced to Ti(0) the active reagent, couples two alkenes that isn’t accessible via Wittig

Question 6

Radical chain reactions

Answer 6

initiation, propagation and termination

Question 7

Radical initiators

Answer 7

AIBN, more convenient that UV light, generates radicals throughout soln

Question 8

Why radical reactions without O2

Answer 8

ground state oxygen is a diradical, reacts with R. to give ROO. radicals, terminating chain growth

Question 9

C-C bond formation with radicals

Answer 9

alkene with BrCCl3 and UV, used for alkene polymerisations, UV cleaves weakest bond first, C-Br, forms .CCl3, initiates radical reaction, .CCl3 adds selectively onto carbon that forms most stable radical

Question 10

intramolecular radical reactions

Answer 10

good for making 5-membered rings