Question

help please. be as specific as possibly please

-sincerley student in need

Model 7: Which H Will Be Replaced by X? In a radical halogenation reaction a halogen (F, CI, Br or I) replaces an H. In most cases there is more than one type of H to choose from. For example the hydrocarbon below has two different types of H's: CH3 сн CHs hy CH or CH Н-С н,с CH3 Н,с X-F, CL, Br or CH3 Three factors determine which H on a hydrocarbon will be replaced: i. The type of H. (benzyl, allyl, 3°, 2°, 1° or methyl) ii. The number of H's of a given type. iii. The identity of X. (We will discuss this on the next page.) First Propagation Step (H Abstraction by X) First Propagation Step (H Abstraction by X) H Abstraction of a 1° H leads to a higher V.E. radical intermediate. But there are NINE 1 H's to choose from! | H н Н. Abstraction of a 3° H gives a lower V.E radical intermediate. Н- н H H H H But there is only ONE 3° H to choose from. Critical Thinking Questions 12. Explain why, for the example above, you would expect a 1:9 ratio of 3 to 1 H substitution products if a 3° radical had about the same potemtial energy as a 1 radical 13. But a 3° radical is LOWER in potential energy than a 1° radical, When X C1, a 3 radical intermediate is 5 times more favorable than a 1° radical intermediate. Given this, explain why, for the example above, a 5:9 ratio of 3° to 1° H substitution products is expected. (Consider both the type of H and the number of identical H's.) LAS

all of the information needed is in the image

Answer 1

H H zi Hydrogen. Hec CHE H 3° Hydrogen identical Hin three marked carbon. In the above molecule there are an -CH3 unit and one 3°11 at the of Now: the 30'#': 1H ratio in the above molecule = 1:9. Ryn. Now, In the process of Radical Halogination . Radical initiatoni EX2 - 1 15+ progation step! снэ et2 + CH e xi + . CH₂ net CH CH s He CH3 Radical Her CH₂ .Radical x ! rmation - Product formy ÇH3 e CHE

re, "2 CH₂-X WE CHE 2 - Now, In the above radical oxon the product formation is depend on the formation of alkyl radical and stability of that radical. Radical + Next, we have to think . cil Stability of Radical:/38 is more stable than the ro Radical certo the intermediates) (13) Statistical Pro bability of_formation of I'Radical & 3? Radical inter mediately which is there are 9, 1°H' available correspond to 1, &'H?). So, probability of formation of 1:3' Radical is 9:1 1. So, in the question it is given to assume that 3° Radical is as stable as 1° radical interne inter mediate So, Product formation will only depend on the Statistical probability of formation of Radical intes mediate , 1°& 3' radical fe, 1:9. That's why, product 3° Substituted: 1' substitud 4 = 1:9.

13. to consider before . In the question 13 you to have the two factor that we discussed a stabilitey of Radical (6) Probability factor. Now, Here in this problem st. given that Stability of 3° Radical is 5 timers larger than 1° radical So, there is chance to form the product 3 subs. H' Substituted product 5 times than 10 % Substituted product. If there present 1,'3'H' and 10? \'H'. Anothers a factor the state's tical factor if we consider this then there is a probability of 1°t Substituted product than the 3° H substituted product by 9 times. If we both constider the both case then the compound ratio of @ 30f'Sustituted prduct : 1° Substituted product will be 5.9. Simultaneously