Chem 21
Homework set 11
End-of-chapter problems from Hornback: Ch 11: 32 - 37, 38 (of course, your syntheses must
(not "may") produce racemic mixtures), 39 - 54.
1. Draw the products of the following reactions, showing stereochemistry where necessary.
Label any products that are enantiomers or diastereomers. As a general rule, don't draw products
formed in insignificant amounts, don't draw the same product twice, and don't write mechanisms.
Of course you should always keep the mechanism in mind — that’s the best way to predict
products.
(a)
(b)
HBr
HCl
(c)
(d)
HCl
HI
(e) Suppose you combined 1 mole of isobutylene (aka 2-methylpropene) and 1 mole of 1-butene
then added 1 mole of HBr. (of course, 2 moles would be needed to use up all of both alkenes,
but we're only adding 1 mole here.) What compounds would you find when the reaction was
over? Draw their structures below.
(f)
(g) How is part f similar to part e?
HI
(1 equiv)
2. Draw the products of the following reactions. Show stereochemistry where relevant, and
label any products that are enantiomers or diastereomers.
(a)
(b)
Br2
(c)
Cl2
(d)
Cl2
Br2
H2O
H2O
(e)
(f)
Hg(OAc)2
NaBH4
Hg(OAc)2
H2O
NaBH4
D2O
(g)
(h)
Hg(OAc)2
Hg(OAc)2
NaBD4
H2O
NaBH4
Et–OH
3. Draw the organic products of the following reactions. Show stereochemistry where relevant,
and indicate any products that are enantiomers or diastereomers.
(a)
(b)
BH3
BH3
H2O2
H2O2
HO– , H2 O
HO– , H2 O
(c)
(d)
BD3
H2O2
1. OsO4
–
HO , H2 O
2. aq. Na2SO3
(e)
(f)
1. OsO4
1. OsO4
2. aq. Na2SO3
2. aq. Na2SO3
4. Write mechanisms for the reactions below, showing each step clearly with curved arrows, as
always. Although they may look completely alien at first, they are just slight variations on the
reactions you've recently learned. So what's the best approach? (i) panic and forget everything
you've learned about skeletal structures, valence, and assigning charges, then draw a swarm of
arrows, wave your hands over the page, and say “poof”; or (ii) pay careful attention to the
electrons and charges, and shift electrons in logical, familiar ways. (hint: pick ii! pick ii!)
(a)
O
H+
OH
H2O
(b)
OH
Br2
H2O
O
Br
Chem 21
Fall 2009
HW set 11
30 points; due Wed, Dec 2
Name _________________________________________
1. Draw the products of the 8 reactions below, including stereochemistry where appropriate.
(Please do not use wedge/dash notation when you're only showing conformation.)
H2
Pd
D2
Br2
Pd
D2O
1. Hg(OAc)2, H2O
1. OsO4
2. NaBH4
2. aq. Na2SO3
HCl
1. BH3
2. H2O2
H2O, HO–
1. Hg(OAc)2
CH3CH2OH
2. NaBH4
2. The following reaction goes via the usual mechanism. Explain why the first product is
formed instead of the second. (A good answer will likely include more structures than words.)
O
H+
ROH
O
O
R
not
R
3. Write a mechanism to account for the following reaction.
O
H+
OH
H2O
(racemic)
4. Suggest synthetic routes that could be used to carry out the following conversions in good
yield. Please do not write mechanisms. Just write the sequence of reactions — starting material,
reagents, and final product — that you would carry out in the lab.
(a)
OCH3
Br
(b)
(racemic)
Br
OH