CHEM 203 HOMEWORK 7 Alkyl halides. 1. Write the structure of an alkyne that contains at least 4 carbon atoms and that:

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1 CEM 20 MEWRK 7 lkyl halides 1. Write the structure of an alkyne that contains at least 4 carbon atoms and that: Produces a chiral diol when treated with 2 and ndlar catalyst followed by s 4 and aq. as e.g. ; ; etc. Produces a chiral dibromide when subjected to a / (liq) followed by 2 e.g. ; ; etc. c. Produces a chiral alcohol when treated with 2 and ndlar catalyst followed by B and 2 2 / aq. a e.g. ; etc. d. Produces an achiral alcohol when subjected to a / (liq) followed by B and 2 2 / aq. a e.g. e. Produces the same bromohydrin when treated with 2 and ndlar catalyst followed by 2 / 2 or with a / (liq) followed by 2 / 2 e.g. f. Produces an achiral diol when treated with 2 and ndlar catalyst followed by s 4 and aq. as, but a chiral dichloride when treated with 2 and ndlar catalyst followed by 2 e.g. 2. The reduction of ozonides with / and the analogous reduction of alkyl azides to primary amines is likely to involve SET chemistry. Write a plausible mechanism for the following reactions: C C C C 2 C C C C C C C radical anion of the ozonide C C C C a zinc alkoxide C C CC 2 C C C C CC CC 2 2 CC CC then:

2 CEM 20 MEWRK 7 p. 2 C C C C C C 2 CC 2 CC CC C C 2 C CC a more sophisticated mechanism envision an initial protonation of the peroxide, because the resultant formal () charge on one of the peroxidic oxygens would greatly facilitate the SET step: C C C C C C CC CC CC C C CC C C CC C C 2 CC CC C C 2 CC CC CC C C C C C C 2 2 CC CC CC 2 C C C 2 C C radical anion of the azide a zinc amide symbol for resonance then: CC CC CC CC 2 2 CC 2 CC CC CC CC

3 CEM 20 MEWRK 7 p.. It is found experimentally that the major product of the reaction of propene with 2, dichloride, is accompanied by small amounts of byproducts such as B-E. Write a plausible mechanism for the formation of -E. 2 (major) B C D E ( others still) minor byproducts compound obviously arises through chlorination of the alkene by the chloronium ion mechanism. Compounds BE appear to be products of radical reactions. So: if some of the 2 were to dissociate (light), then 2 and now... weaker allylic 's resonance-stabilized allylic radical B any of the 's in may undergo radical substitution by C D E and, of course: B C

4 CEM 20 MEWRK 7 p Write accurate mechanisms for the following reactions: K., then / the final product must have formed from an alkene that has the following structure: = reconnect therefore: = K E2: antiβ-elimination, = C C heat C first: C heat then:

5 CEM 20 MEWRK 7 p. 5 = C top-face attack C C C ± ± C products of S 1 C bottom-face attack C = C the carbocation is a strong onsted acid product of E1 5. Propose a method to achieve the transformations shown below. ote: it is understood that chiral products will be formed as racemates. BS, hν 1. B aq. a K, rad. init. a, 2 c. C d., rad. init. ac 2, hν K 1. B aq. a C e. f. SC 2, hν K BS, hν ac 2 S 4, heat asc

6 CEM 20 MEWRK 7 p Complete the following reaction diagrams by indicating missing reagents / starting materials / products and write accurate mechanisms for each step. ote: by convention, chiral products are represented as single enantiomers, with the understanding that in fact they will be formed as racemates. 1. 2, hν 2.. C C= 4. Mild 1. K 2. 2, 2. a c. d C 2. C Sa 1. BS, hν 2. Mg. C 2 4. Mild C C S mechanisms: hν 2 SET 2 2 C C E2 2 ± == a 2 c. C C ± C C Sa S 2 C C S

7 CEM 20 MEWRK 7 p. 7 d. contaminant in BS ± hν 2 Mg Mg Mg Mg Mg C Mg Mg 2 7. Propose a good method for the preparation ("synthesis") of compounds -k. starting LY with 1-butene as the source of carbon atoms, plus any additional reagent that might be needed (, borane, Mg, ) c. d. e. k. j. i. h. C f. g. 2 2 S 4 2 S C, then, rad. init. c.

8 CEM 20 MEWRK 7 p. 8 d. this compound is an alkane alkanes may be prepared by S 2 reactions of halides with organo- or -Mg reagents assisted by Cu(I) a synthesis based on this principle may proceed as follows: part part c. Cu e. part c. Mg Mg part mix, then mild f. part part Cu g. part, then 2 2, C h. s 4, then part aq. as BS i. part d. hν j. B, then 2 2, aq. a k. part part mix, then mild