Question

Step Question/Exam 3: Draw a radical mechanism for the following photohalogenation reaction Brg t th to you ? + H-Br UV light (h) 90% UV-light and a halogen...these are great radical initiation conditions! 1.) Look for a weak bond that would be able to homolytically cleave to form two radicals Draw the resulting radicals: 2.) Identify the most stable site for a radical to sit. Your product distribution will predict where this is FYI. Again, the reactivity of radicals is pretty similar to carbocations (both are missing 1 or 2 e) Hint: there are three sites. Draw and label: Primary, secondary, or tertiary radical as appropriate: Circle the most stable. Let's use this for our first product forming step 3.) Draw a radical mechanism: Use the radical you created in step 1.) to pick off a hydrogen to form the H-Br to create the most stable carbon radical. Remember that only one electron transfers with it, and the other stays behind. Use your "fishhook" arrows (single headed arrows) to indicate this: 4.) Now that you have a stable carbon-centered radical, what will it do? Remember that radicals like to preferentially react with other radicals if they are present. Are there any other radicals around? 5.) You can do similar pathways to explain your minor products. This is another example where chemistry is a bit "messy but shows that these selectivity patterns can be quite subtle.

Answer 1

No Bra LBG B +H07 to uvlight (hi) al die A 904. 87. 20 21.1 under er light the halogen Br2 homolytically cleaned - B homolyn's ror honglysis 2. Brand 2) The radical formed is Br which now attack the alkane and form the carbon radical. the carbon radical follows the same ore des of stability as well Carbo cation i.e.; 3°>20) 10 (all R-H & Br Ř & HBO R = is the belowgroup which have different site form different T radical , . primary tertiary roles Secondray in world!

greater no. of hy perconjugable 3" is most stable due to lydrogen. + H BY hefit - Ý + ABY BX is formed by breaking of c-th bond. the most stable radical 3 Bo 7 Now carbon radical react with + 37 t ractor for at chain propagation step. hitoon Char - Bi orarios — Luo *e H formed very en and less stable radical will be product from it also less.