1.5 h; 100 points Signature UM ID # Problem Points Score GSI I 17 II 20 III 20 IV 19 V 24 Total

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1 hemistry 10 First ame First Examination Last ame May 0, 01 please print clearly 1.5 h; 100 points ignature UM ID # PRIT TE FIRT LETTER F YUR LAT AME ERE: Problem Points core GI I 17 II 0 III 0 IV 19 V 4 Total omplete Lewis structures are required unless you are given other specific instructions. Precision in drawing counts. heck all three-dimensional representations to ensure you are implying an unequivocal direction of bonding. Do not forget to include important features such as nonbonding electron pairs and formal charges when appropriate. Individual point values are given in the corner of each answer space. The exam has pages in addition to this cover page. A pka table is on the last page.

2 I. (17 points) A. ame Page 1 onsider the heterocylic aromatic compounds (the best of a set of possible resonance contributors is shown for each): xazole pk a of conjugate acid is ~ 0.8 Imidazole pk a of conjugate acid is ~ 7 (a) Assuming the hybridization model for all atoms, provide an accurate and complete threedimensional orbital picture for the best resonance contributor of oxazole. As always, you should use lines, dashes, wedges, p orbitals (lone or overlapping) to show the direction of all electrons (or empty orbitals) in your drawing. All bond angles should reflect the appropriate geometry and hybridization chosen for your drawing. (b) omplete the following sentence by circling the best word. xazole is a stronger weaker similar base compared to imidazole. circle one (c) xazole and imidazole will interact via a very strong hydrogen bond. Using the structure of imidazole provided, draw in a molecule of oxazole, and clearly show the best possilbe hydrogen bond that can form between these two using. B. Imidazole is very versatile as a reactant. Predict the product(s) that are most likely in each of the following situations and balance your reactions! (a) K (b) l l Al l

3 II. (0 points) ame Page A. onsider Molecule 1 shown below. For each of the other drawings, pick the letter for the best choice from the list of "Descriptors" to describe if and how the other drawing is related to the structure labeled as 1. 1 Descriptors the same resonance A form as 1 a different resonance B form for 1 D E F a structural isomer of 1 a conjugate acid of 1 a conjugate base of 1 is not related to 1 i) compared to 1, this is: ii) compared to 1, this is: iii) compared to 1, this is: iv) compared to 1, this is: v) compared to 1, this is: vi) compared to 1, this is: B. Working with the same molecular formula as in Molecule 1 above ( 5 ) draw valid and complete Lewis structures (i.e. show all electrons) with the following criteria: This compound contains: 1) all closed shell atoms ) no atoms carry formal charge ) a ring containing only 4 atoms 4) a carboxylic acid functional group This compound contains: 1) all closed shell atoms ) no atoms carry formal charge ) a ring containing only 4 atoms 4) neither oxygen can be a hydrogen bond donor 4 4

4 III. (0 points) ame Page alicylic acid is an important ingredient used in the production of aspirin (aka, acetylsalicylic acid). It is a diprotic acid, and the pk a s of its protons are ~ and ~8. Use your pk a table to assign these actual values to the appropriate acidic protons on salicylic acid. salicylic acid A. (a) Provide the complete curved arrow mechanism, draw the products and evauate the Keq for the reaction that occurs when salicylic acid is treated with one equivalent of the the base diethylamine. curved arrow mechanism (b) K eq = 10 (c) 4 B. (a) In aqueous solutions at a p of 7.5, salicylic acid exists as a mixture of two compounds (protonated and deprotonated forms), one at a higher concentration than the other. Draw these two compounds in their appropriate boxes. higher concentration lower concentration (b) The reaction scheme depicted below is part of the process used in the manufacture of aspirin. Provide the missing information (curved arrows, intermediates as needed) in this chemical transformation. :B and -B + represent general Bronsted bases and acids available and used in every step. B B salicylic acid

5 IV. (19 points) ame Page 4 The chemical imatinib, shown below, has been used to treat a number of cancers (most successfully hronic Myelogenous Leukemia). When evaluating the structure of this compound, please remember to take into account all other major and valid resonance contributors (as always). ATM 1 (a) For each of the atoms indicated with an arrow, provide the atom's most reasonable hybridization as well as its electronic geometry (VEPR), and observable geometry (shape). ATM ybridization Electronic geometry bservable geometry ATM 1 ATM ATM ATM ATM 4 imatinib ATM 4 (b) Ima-1 (shown below) represents a small molecular "section" that is found within imatinib. Its reactivity and structure can be best explained with a set of resonance contributors. Draw all other resonance contributors for this structure that contain all closed shell atoms and atomic formal charges between +1 and -1. Ima-1 (c) Another "section" of imatinab, Ima-, is shown below. ii)t/f More nitrogen atoms carry partial negative charge in Ima- than they do in X. The - bond indicated by the arrow is longer in Ima- than it is in X. - Ima- - X Ima- has units of unsaturation. Ima- and X share the same molecular formula. There are more sp hybridized carbon atoms in Ima- than there are in X. 5

6 V. (4 points) A. ame Page 5 Fill in the missing curved arrow mechanisms for each step in the production of malate, a key reaction in the breakdown of carbohydrates. ote how water plays important roles in this (and many other) biological reactions. (a) (b) B. yanamides are organic compounds used widely in pharmaceuticals. (a) Draw the complete set of Lewis structures (resonance contributors) for cyanimide, the connectivity is shown below. All atoms are closed shell, and atomic formal charges are +1, 0, or -1. connectivity of cyanamide resonance contributors. (b) Use your resonance contributors to make predictions about geometry and hybridization of the atoms indicated with arrows. Assuming the hybridization model for all atoms, provide an accurate and complete three-dimensional orbital picture for the best resonance contributor of cyanamide. As always, you should use lines, dashes, wedges, p orbitals (lone or overlapping) to show the direction of all electrons (or empty orbitals) in your drawing. All bond angles should reflect the appropriate geometry and hybridization chosen for your drawing. ybridization connectivity of cyanamide ybridization VEPR geom

7 AID (trongest Acid) l I l F pk a JUGATE BAE (Weakest Base) -1 l -7. I l -4. F AID l l l pk a JUGATE BAE l l l (Weakest Acid) (trongest Base)

1.5 h; 100 points please print clearly Dr. Kathleen Nolta Signature UM ID # Problem Points Score GSI I 24 II 19 III 20 IV 21 V 16 Total 100

1.5 h; 100 points please print clearly Dr. Kathleen Nolta Signature UM ID # Problem Points Score GSI I 24 II 19 III 20 IV 21 V 16 Total 100 hemistry 0 First ame First Examination Last ame.5 h; 00 points please print clearly Dr. Kathleen olta ignature UM ID # PRIT TE FIRT LETTER F YUR LAT AME ERE: Problem Points core GI I 4 II 9 III 0 IV V