Cl 7 8 N 9 H 6 HS 4. 2-(5,5-dimethyl-3-chlorocyclopent-2-enyl)-5-oxo-6-methyl-7-cyanoheptyl 2-hydroxy-3,3-dimethyl-4-(1-mercapto-

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1 hem 0 Sample Midterm Beauchamp Exams are designed so that no one question will make or break you. The best strategy is to work steadily, starting with those problems you understand best. Partial credit is given for anything done correctly, but no points are given for incorrect answers. Make sure you show all of your work. Draw in any lone pairs of electrons, formal charge and curved arrows to show electron movement where appropriate. Do your best to show me what you know in the time available.. Provide an acceptable name for each of the following molecules. a b 7 -phenylbut-e-enoic -benzylpent--ynoic anhydride c S 8 7 -mercapto--amino--methoxy--cyano-- (cycloocta-z,e-dienyl)hexanamide l e -hydroxy--formyl-,7-dioxo--ethoxyhept-z-enoic acid d l l S -chloro--oxo--cyano--mercapto-7-aminonon-z-en-8-ynoyl chloride 7 S -(,-dimethyl--chlorocyclopent--enyl)--oxo--methyl-7-cyanoheptyl -hydroxy-,-dimethyl--(-mercapto- -propoxy--aminohex--enyl)-,-dioxo-7-(-methylethyl)-8-(-propylbut--ynyl)-9-formyldodec-z-en-0-ynoate

2 . Draw an acceptable Lewis structure (D) for the following molecule. Show all single, double and triple bonds with one, two or three lines. Include all lone pairs of electrons as two dots. Include any formal charge, if present. Identify any functional groups by name (i.e. ketone, amide, etc.) ( ) () amide alkene ketone ester alkyne aldehyde ammonium ion ether alcohol nitrile carboxylic acid. Draw a -D structure for the following molecule. Show bonds in front of the page as wedges, bonds in back of the page as dashed lines and bonds in the page as simple lines. Show orbitals for pi bonds and lone pairs along with their electrons. Identify the hybridization, bond angles and descriptive shape for all numbered atoms. ( ) Atom Shape ybridization Bond Angles # bond # bonds # lone pairs linear sp 80 trigonal planar sp 0 0 linear sp 80 0 trigonal planar sp 0 tetrahedral sp 09 0

3 . Write all reasonable D resonance structures for the following formulas. Include formal charge where appropriate and use proper curved arrows to show electron movement. Draw at least resonance structures in D. no resonance in this pi bond

4 . Draw an example of each of the following. Use as a carbon portion for unspecified parts of your structures.. methyl. methylene. methine. primary. secondary. tertiary 7. quarternary 8. isopropyl 9. isobutyl 0. sec-butyl. t-butyl. neopentyl. vinyl. allyl. propargyl. phenyl 7. benzyl 8. primary amine 9. secondary amine 0. tertiary amine. quaternary ammonium ion. methyl. primary = o 0. sec-butyl. methylene. secondary = o. t-butyl. methine. tertiary = o 7. quaternary = o 8. isopropyl. neopentyl 9. isobutyl. vinyl. allyl

5 . propargyl. phenyl 7. benzyl 8. o amine 9. o amine 0. o amine. o ammonium ion. Use the given formula ( l S) to draw a molecule with the following functional groups: carboxylic acid, anhydride, ester, acid chloride, amide, nitrile, aldehyde, ketone, alcohol, thiol, amine, ether, chloro, alkene, alkyne and aromatic. Identify each functional group by name. What is the degree of unsaturation? ether ester alcohol thiol S acid chloride l carboxylic acid alkyne alkene amide aromatic ketone nitrile anhydride amine aldehyde l chloro l S degrees of unsaturation = [()++ - ()] / = (7 - ) / = 7 degrees 7. Use the given formula ( 8 ) to write examples of each kind of isomerism: skeletal, positional, conformational, enantiomers, diastereomers. ( 8 ) skeletal isomers positional isomers S conformational isomers S enantiomers E S diastereomers Z diastereomers

6 8. Match the given boiling points with the structures below and give a short reason for your answers. (-7 o, + o, +80 o, + o, 0 o ) -butanone -methyl--butene propanoic acid Kl potassium chloride -methylpropene MW = 7 g/mol MW = 70 g/mol MW = 7 g/mol MW = 7. g/mol MW = g/mol 0 o + o -7 o +80 o + o Structure has ionic bonds, by far the strongest forces to overcome and has an extremely high bp. Structure has strong bonding possiblities and the second high bp. Structure has polar = bond so higher than structures and, which only have weak dispersion forces. Structure is larger and has a larger surface area and more dispersion forces than structure, so has a higher bp. 9. a. exane (density = 0. g/ml) and water (density =.0 g/ml) do not mix. Which layer is on top? Why don t they mix? b. arbon tetrachloride (density =.9 g/ml) and water (density =.0 g/ml) do not mix. Which layer is on top? hexane water =.8 D = 0 D Differences in polarity keep these two from mixing and water is more dense than hexane and sinks to the bottom. b water carbon tetrachloride l l l l = 0 D =.8 D Differences in polarity keep these two from mixing and carbon tetrachloride is more dense than water and sinks to the bottom. 0. The melting point of al is very high ( 800 o ) and the boiling point is even higher (> 00 o ). Does this imply strong, moderate or weak forces of attraction between the ions? onsidering your answer, is it surprising that al dissolves so easily in water? Why does this occur? onsider another chloride salt, Agl. ow does your analysis work here? What changed? Lattic structure - depends on the size and charge of the ions. Each ion is surrounded on many sides by oppositely charged ions. To introduce the disorder of a liquid (melt) or a gas (boil) requires a very large input of (mp indicates the amount of required to break down the ordered lattice structure and boiling point indicates the amount of required to remove an ion pair from the influence of all neighbors. Ionic bonds (ionic attractions on all sides) can only be bronke at great expense in.

7 owever, many water molucules working together can break down this structure by solvating both the cations and anions (solvation ). When solvation > lattice, the salt will dissolve (al). When solvation < lattice the salt will not dissolve (Agl). al Agl lattice solvation lattice solvation Small difference between two very large values. G = dissolves G = does not dissolve. Draw all possible chair conformations of cis--phenyl--methylcyclohexane and trans--phenyl-- methylcyclohexane. Which conformation is more stable? Draw it first. Provide a reason for your answer. Draw ewman projections of the most stable and least stable conformations using the and or the and bonds to sight along. Point out any gauche interactions shown in your ewman projection. Use the table on the next page to determine the gauche costs. Using the trans--phenyl--methylcyclohexane what are the relative percents of each conformation? Sketch an diagram that shows how the changes with the conformational changes for that isomer. trans isomer A = most stable conformation B = least stable conformation flip flop costs = gauche interaction =. kcal/mole cis isomer costs = axial phenyl =.9 kcal/mole = gauche interaction =. kcal/mole total =. kcal/mole Gauche groups crowd one another. most stable isomer flip flop costs = axial phenyl =.9 kcal/mole = axial methyl =.7 kcal/mole total =. kcal/mole costs = axial methyl =.7 kcal/mole = gauche interaction =. kcal/mole total =. kcal/mole ewman projections of trans conformational isomers D ewman projection relative stabilities = A > D > > B K eq = 0 least stable isomer G,00.T,80 = 0 -. B = 0 = 0 = A A = kcal mole B = +. Larger axial groups crowd the other axial positions on the same face.

8 . Use a ewman projection of the bond of -methyl--phenylhexane to show the most stable conformation first. otate through all of the eclipsed and staggered conformations. Using the values provided in the table below, calculate the relative energies of the different conformations. Plot the changes in in the graph diagram provided. int: Draw a D structure first and bold the bond viewed in your ewman projection, then decide your line of sight. What is the relative percent distribution between the lowest conformations? Approximate Eclipsing Energy Values (kcal/mole) Me Et t-bu Approximate Gauche Energy Values (kcal/mole) Me Et t-bu Me Et Me Et methyl--phenylhexane G K eq = 0 -.T t-bu t-bu most stable -methyl--phenylhexane Use the bond o 0 o 0 o 0 o 0 o Et Et Et Et Et K eq = 0 G 00.T,80 = 0 = = = isomer isomer Et least stable potential kcal.0 mole.0 most stable rotational angle 0 o 0o 0 o 80 o 0 o 00 o

9 . For the following set of Fischer projections answer each of the questions below by circling the appropriate letter(s) or letter combination(s). int: edraw the Fischer projections with the longest carbon chain in the vertical direction and having similar atoms in the top and bottom portion. lassify all chiral centers in the first structure as or S absolute configuration and write an acceptable name for that isomer. l l l l A B D E S meso l l l l S a. Which are optically active? A B D E b. Which are meso? A B D E c. Which is not an isomer with the others? A B D E d. Which pairs are enantiomers? AB A AD AE B BD BE D E DE e. Which pairs are identical? AB A AD AE B BD BE D E DE f. Which pairs are diastereomers? AB A AD AE B BD BE D E DE g. Which pairs, when mixed in equal amounts AB A AD AE B BD BE D E DE will not rotate plane polarized light? h. Draw any stereoisomers of -bromo--chlorobutane as Fischer projections, which are not shown above. If there are none, indicate this. A not shown B = E l l l l i. Would anything change if, in compound D, the was replaced with a l group? ow about compound A? ompound D would not be meso and become chiral. ompound A is chiral and would still be chiral. j. The structure of lucknolide B was recently determined (and the absolute configuration of all chiral centers!). It was isolated from the terrestrial bacteria, Streptomyces sp. AK-89, in screenings for new medicinal lead compounds (rg. Lett. p.800, 00). ircle all chiral centers and any other stereochemical features, and calculate the maximum number of stereoisomers possible. lucknolide B one of two related compounds * * * * * * This ring is too small to have a trans double bond. * = chiral center 7 chiral centers # possible stereoisomers = 7 = 8