Unformatted text preview: 1. Squaric acid (below) is a very acidic organic compound. Chem 322a 9/8/10 a. Using resonance structures, explain why squaric acid is more acidic than cyclobutanol. O HO O OH b as e O HO O O O HO O O s qu ar ic ac id re so na nc e sta biliza tio n of a nion b as e OH cy c lob utano l O n o r es ona nc e b. Draw all four resonance structures for the dianion of squaric acid. Would you expect this second proton to also be acidic? Yes, squaric acid’s second proton is very acidic due to resonance stabilization of the dianion. For squaric acid, pKa1 = 1.5, pKa2 = 3.4. 2. (6 pt) Write the functional group of each of these compounds underneath their structures, including 1°, 2° or 3° as appropriate. H N Br OH 2 amine ° 3 alkyl halide or haloalkane ° 2 alcohol ° 1 3. Write an equation for the Lewis acid/Lewis base reaction between boron trifluoride and dimethyl sulfide (CH3)2S. Show formal charges if present and use curved arrows to track the flow of electrons. F FB F S F FBS F 4. Provide a plausible synthesis for this molecule using any necessary reagents. OH 1. 2 equiv. NaNH2 2. D2O OD D OT D 1. NaOtBu 2. T2O Hydride (H:-) could also be used for the first step. 5. Order the following from strongest to weakest acid. H O N OH H N H N a. b. c. d. e. (most acidic) a. > d. > c. > e. > b. (least acidic) 2 6. For each of these 5 reactions, fill in the boxes with the correct arrow indicating the direction of the equilibrium and circle the stronger acid. a) CH3CH2 S ++
H3 C S SH CH3CH2SH S +
H3 C S - b) P H3 ++ +
++ AsH2 - + PH2 - + AsH3 c) H2Te -SH -TeH + H2S O
d) Cl3C S
e) O - ++ +
H3 C O OH Cl3C O OH +
H3 C O O - S ++ + S S S S + - 7. Indicate which acidity trend (for example, “bond strength”) you applied to answer a) through e) in question 6. a) resonance stabilization b) bond strength c) bond strength d) inductive effect e) resonance stabilization 3 ...
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- Spring '10
- Organic chemistry, Trigraph, Tió de Nadal, Squaric acid, acidic organic compound.