1. Fundamentals (a) (10 points) Fill in any hydrogens not shown and indicate the molecular formula of the compound in the box provided. (b) (10 points) Draw a Lewis structure for each of the following molecules. Be sure to include all lone pair electrons and circle all formal charges, where appropriate. Lewis Structure (line-bond) ybridization of Central Atom ame of Geometry Carbonate (C 3 2- ) Chloroform (C 3 ) (c) (10 points) Indicate the hybridization on the indicated atoms on prednisone and methyl azide. X Yet Prednisone it it it I Cgy Asch It iii or d d Ci ime I too 1 I Ci 00 o_ Il i Sp2 trigonal planar s 3 C 3 tetrahedral Methyl azide 2 1
2. Resonance and Formal Charge I 12 RA ang (a) (6 points) Add formal charges to all charged atoms below. Lone pairs are provided on carbon where applicable, but lone pairs on heteroatoms are implied (add them yourself). Circle the charge and make sure it s clear to which atom the charge belongs! C 3 2 C 0 0 2 C P to C3 C 3 (b) (24 points) Draw two additional resonance structures for each compound below and use curved arrow notation to show electron movement. Indicate (circle) whether each new structure is equivalent or non-equivalent to the original provided structure. All hydrogen atoms are drawn on the provided structure, but it is not necessary to draw all s in your answers. Lone pairs are not shown on heteroatoms ( and ). equivalent / non-equiv. equivalent / non-equiv. g arrows 0 2ptsarrowset 3 C a eachwronglextracharge And video explofeating 8 a q Ia equivalent / non-equiv. many other possibilities If o 00 equivalent / non-equiv. 2 not possible K equivalent noequivalent structures possible
3. Acidity (a) (8 points) The following compounds are listed in order of acidity (most acidic on the left). Indicate the approximate pka value that belongs to each compound in the boxes provided. + 3 + 4 2 3 C 4 (b) (8 points) Rank the following sets of molecules in terms of acidity where 1 is the most acidic. Give your numerical answer in the box provided under each. There are no ties! Set 1 Set 2 Acetone (pka 19) F 7 5 10 16 19 35 50 2,4-Pentanedione (pka 9) 16 5 Phenol (pka 10) 46 5 Br F F Acetic Acid (you should know this pka!) 4 2 3 I 4 3 5 2 6 I 16 Br 5 7 pka (c) (24 points) For each reaction, label the acid and base (circle one), use curved arrows to indicate electron movement between reactants, draw the products, labeling the conjugate acid / base (circle one), and finally predict the direction of the equilibrium. K + 3 C f a 2 zcz direction a acid / base acid / base of equilibrium conjugate conjugate. acid / base acid / base + direction of equilibrium doo acid / base acid / base conjugate acid / base T conjugate acid / base 3
4. omenclature and Functional Groups (a) (10 points) Circle and identify every functional group in the fictitious molecule below. effegthmatters ddeht 00 alkene S amine ester C 3 ther ketone amide (b) (20 points) Draw skeletal structures of any three of the following. Draw a large X over the part to skip, otherwise (i) - (iii) will be graded. (i) 4-Ethyl-2,2-dimethylhexane TTT r thiol 0 caraabgoxylic alkyne 7pts qqfts.gg e (ii) cis-1-cyclopentyl-3-bromocycloheptane Q xttt sabr (iii) trans-2-tert-butyl-1-chlorocyclopentane (iv) 4-Isopropyl-3-methyloctane a Ttr 4
A A 5. Stereochemistry (a) (10 points) Chiral centers are important for metabolic function by providing the ecific 3D shape needed to fit into a receptor or enzyme active site. Indicate the chiral centers (AKA stereogenic centers) with a star (*) on the two naturally occurring molecules below. Ipt each Iper extra incorrect Prednisolone S Biotin C 2 (b) (8 points) There are four stereoisomers of pseudoephedrine (A D below). The (S,S) isomer is the commercially available decongestant Sudafed. Designate each chiral center as R or S in the boxes provided. lpbox e s 3 C s R A s B C 3 R S R C 3 C D C 3 zpts (c) (12 points) Indicate whether the indicated pairs from (b) are enantiomers or diastereomers. A & B A & C each enantiomers diastereomers diastereomers B & D (d) (5 points) Draw a constitutional isomer of Sudafed. enantiomer C & D C3 4172 TEI'T any Gottis F compound with l I cz many possible answers tf different bonds than any.ve 5 kz
6. Conformational Analysis (a) (20 points) Consider the following compounds: cis- and trans-1-tert-butyl-3-methylcyclohexane Draw the skeletal structures and two chair conformations of each. Use the provided templates for the cis compound and draw new chairs for the trans compound. Indicate the more stable conformation of each compound and briefly explain the relative stabilities of the conformations (not necessary to use complete sentences!). cis-1-tert-butyl-3-methyl cyclohexane trans-1-tert-butyl-3-methyl cyclohexane (b) (15 points) Consider the rotation around the C3-C4 bond of 2,2-dimethyl-4-chlorobutane. Site down the C3-C4 bond and draw the least stable and most stable conformations of this compound in ewman projections. You may draw other ewman projections as well, as long as the least and most stable are clearly circled and labeled. Briefly explain the relative stabilities of these conformations (not necessary to use complete sentences!). if TIME 2,2-dimethyl-4-chlorobutane "down the C3-C4 bond" 1 Y yess stable 1,3 diaxialinteractions b w EButyl Me I a c i ring flip 6pts explanation target Butylgrp 110 causetgreater more stable 1 o no 4Idiaxial stain withequatorial substituents smaller1,3 diaxial strain 1,3 daxial interactions wfmeglarger grp equatorial Ici I d leaststable moststable beftpffation dueto torsimdsrainn.fr ayf hlmsw between lo mps 6 1argeg_rps far apart