17. Is allobetulin chiral? Why or why not? (2 points) 21. How many stereoisomers exist for allobetulit? ( 2 points) Allebetulin is chiral because it is nonsuperimposable on its mirror image. 18. How many stereoisomers are possible for betulin? (2 points) 22. Draw one diastereomer of the allobetylin structure shown below. (2 points) 19. Draw the mirror-image stereoisomer of betulin shown below. What is the stereochemical relationship between the two images? ( 2 points) 23. Betulin is a triterpene. Explain what this means. (2 points) 20. Draw one diastereomer of the betulin structure shown below. ( 2 points) 24. Circle two isoprene units of the betulin structure shown below. (2 points)