Chapter 31: Q26P. (page 1258)
Locate the isoprene units in each compound.
(a)
(b)

(c)

(d)

(e)
(f)

(g)

(h)

Short Answer
(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

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Chapter 31: Q26P. (page 1258)
Locate the isoprene units in each compound.
(a)
(b)

(c)

(d)

(e)
(f)

(g)

(h)

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

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(a) Draw a skeletal structure of the anabolic steroid methenolone from the following description. Methenolone contains the tetracyclic steroid skeleton with a carbonyl group at C3, a hydroxyl group at C17, a double bond between C1 and C2, and methyl groups bonded to C1, C10 and C13. (b) Add wedges and dashed wedges for all stereogenic centers with the following information: The configuration at C10 is R, The configuration at C13 is S, the configuration at C17 is S, and all substitutents at ring fusions are trans to each other. (c) Draw the structures of Primobolan, the product formed when methenolone is treated with and pyridine. Primobolan is an anabolic steroid that can be taken orally or by injection and has been used illegally by well-known Major League Baseball players.
Why are phospholipids, but not triacylglycerols, found in cell membranes?
An isoprene unit can be thought of as having a head and a tail. The 鈥渉ead鈥 of the isoprene unit is located at the end of the chain nearest the branch point, and the 鈥渢ail鈥 is located at the end of the carbon chain farthest from the branch point. Most isoprene units are connected together in a 鈥渉ead-to-tail鈥 fashion, as illustrated. For both lycopene (Problem 31.26), and squalene (Figure 31.9), decide which isoprene units are connected in a head-to-tail fashion and which are not.

Unlike many fats and oils, the cocoa butter used to make chocolate is remarkably uniform in composition. All triacylglycerols contain oleic acid esterified to the OH group of glycerol, and either palmitic acid or stearic acid esterified to the OH groups. Draw the structures of two possible triacylglycerols that compose cocoa butter.
(a) Draw a skeletal structure of the anabolic steroid 4-androstene-3, 17-dione, also called 鈥渁ndro,鈥 from the following description. Andro contains the tetracyclic steroid with carbonyl groups at C3 and C17, a double bond between C4 and C5, and methyl groups bonded to C10 and C13.
(b) Add wedges and dashed wedges for all stereogenic centers with the following information: the configuration at C10 is R, the configuration at C13 is S, and all substituents at ring fusions are trans to each other.
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