CHEM_LAB_KRI_STIN - Answer Sheet Name Partners Question 1...

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Answer Sheet Name: ________________________________________________ Section: __________________ Partners: Question 1 Table . Estimation of pK a of acetic acid using Spartan. Acetic Acid Electrostatic Potential Map Insert your electrostatic potential map (follow the directions in the tutorial, but be sure to clearly show the acid hydrogen and make it 1.2" in width) “Maximum Potential” 68.9987 Calculated pK a 4.13 Literature pK a 4.76 Trifluoroacetic Acid “Maximum Potential” 91.235 Calculated pK a -.984 Propionic Acid “Maximum Potential” 63.7203 Calculated pK a 5.344 Trichloroacetic Acid “Maximum Potential” 90.25 Calculated pK a -.7575 Chloroacetic Acid “Maximum Potential” 77.4122 Calculated pK a 2.1952 Question 1 Analysis . 1) For acetic acid, how well does the calculated pK a agree with the literature pK a ? It was very close due to the pre-lab. Only about .003 off as a rough estimate. 2) For acetic acid, comment on whether the area of maximum positive charge in the electrostatic potential map agrees with what you would expect (what would you expect?) Yes I would expect hydrogen to have a positive charge. 3) Based on what you know about acidity, what is the expected order of acidity (from most acidic to least acidic)? Why is this order expected? The higher the electronegitivity the more acidic would be my general hypothesis. 4) What is the calculated order of acidity (from most acidic to least acidic)? How does this match the expected trend? The most acidic compounds have a lower pka value.
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Question 2 Table . Modeling of acetate using Spartan. Acetate Electrostatic Potential Map Insert your electrostatic potential map (follow the directions in the tutorial, but be sure to clearly show the acid hydrogen and make it 1.2" in width) C=O bond distance 1.248 C–O bond distance 1.251 Charge on oxygen of C=O bond -177.5 Charge on oxygen of C–O bond -178.5 Question 2 Analysis . 1) How do the charges on oxygen and the electrostatic potential map agree/disagree with what is expected? (be sure to comment on what you would expect based on the resonance contributors) The bond legnth was not equal for one of the oxygens, however the chargers were all the same. Which was somewhat counterintuitive for me to grasp.
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CHEM_LAB_KRI_STIN - Answer Sheet Name Partners Question 1...

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