Br Br Br A

Please show the mechanism with arrow formalism.

Jj.168.

(a) CH₂CHCH2CH2CH3 CH3 (b) CH₂CHCH2CH2CHCH₂ CH3 CH3 (c) CH3(CH2), CHCH2CH3 CH2CH3

Four isomers A-D with the formula C5H12O exhibit different reactivity patterns as indicated below. Isomer A reacts with PCC and CrO3 to provide identical products.   Isomer B reacts with PCC and CrO3 to provide different products.   Isomers C and D do not react with either PCC or CrO3.   Isomers A, B, and C readily react with NaH but D does not show any reactivity with NaH.     The 1H NMR splitting patterns for these isomers are as follows.     Isomer A: δ 0.91 (d, 3H), 0.90 (d, 3H), 1.18 (d, 3H), 1.92 (dqq, 1H), 3.38 (dq, 1H), 3.58 (bs, 1H). Isomer B: δ 1.25 (s, 9H), 3.45 (s, 2H), 3.65 (bs, 1H). Isomer C: δ 0.90 (t, 3H), 1.44 (q, 2H), 1.24 (s, 6H), 3.65 (bs, 1H). Isomer D: δ 1.10 (t, 3H), 1.13 (d, 6H), 3.19 (septet, 1H), 3.50 (q, 2H).   Based on all of this information, provide the structures of A-D.  (Note: If there is a chiral center on any of these molecules, assume the stereochemistry as “R”.  dqq=doublet of a quartet of a quartet, bs=broad singlet)

(A) Which triene has the smallest heat of hydrogenation? Explain why. (B) Which triene can be reactive in the Diels-Alder reaction? (C) Which triene is the most reactive in the Diels-Alder reaction?

Arrange the following in order of increasing stability A B D

For each section, circle the mechanism from the two options given and draw the main organic product resulting from that mechanism. Indicate the stereochemistry and if two configurational isomers form, draw both.

The shrub ma huang (Section 5.4A) contains two biologically active stereoisomers—ephedrine and pseudoephedrine—with two stereogenic centers as shown in the given structure. Ephedrine is one component of a once-popular combination drug used by body builders to increase energy and alertness, whereas pseudoephedrine is a nasal decongestant. a.Draw the structure of naturally occurring (−)-ephedrine, which has the 1R,2S configuration. b.Draw the structure of naturally occurring (+)-pseudoephedrine, which has the 1S,2S configuration. c.How are ephedrine and pseudoephedrine related? d.Draw all other stereoisomers of (−)-ephedrine and (+)pseudoephedrine, and give the R,S designation for all stereogenic centers. e.How is each compound drawn in part (d) related to (−)-ephedrine?