1 30 pts Provide an example for each of the following terms Use structures where appropriate 5 pts each a A polar covalent bond C Cl C F H Cl C O b A typical Br nsted acid HCl H2SO4 CH3COOH c The line angle drawing of the linear constitutional isomer of n butane d A cycloalkane in which C H bonds on adjacent carbon atoms are always eclipsed cyclopropane e A cycloalkane that is strain free cyclohexane f A molecule that has a linear shape diamtomic molecules carbon dioxide acetylene acetonitrile 2 of 8 2 Lewis structures and resonance 20 points a For the ion shown draw two valid resonance structures and CIRCLE the more important contributor Use the curved arrow formalism to indicate electron movement 6 points CH2OCH3 H H CH 3 C CH 3 C O O H H b Draw resonance structures for the ozone molecule O3 Is the length of each O O bond in ozone longer or shorter than that of the O O double bond in molecular oxygen Use the curved arrow formalism to indicate electron movement 6 points O3 O O O O O O The length of the O O bond in ozone is longer than the O O double bond of O2 2 pts c Use VSEPR model to predict the shape and hybridization of the atoms in highlighted boxes a b and c in the following structure 8 points O H H C C box a box b C C H H box c box a shape trigonal planar hybridization sp2 box b shape linear hybridization sp box c shape tetrahedral hybridization sp3 3 of 8 3 Organic molecules 20 pts a Draw the line angle formulas of all isomeric alkanes of molecular C5H12 CIRCLE the isomer with the lowest boiling point and BOX the one with the highest boiling point No explanation is needed 6 pts b Within each of the following sets CIRCLE the two structures that represent the same compound 6 pts Set 1 H CH 3 H H H H H H H H CH 3 Set 2 H CH2CH2CH 3 H CH2CH 3 H 3C CH 3 H c In the in the following four molecules CIRCLE the one molecule that you expect to have a dipole moment of zero 4 pts CHCl 3 CH2Cl2 BF 3 NH 3 d CIRCLE the solvent in which cyclohexane would have the lowest solubility 4 pts O OH pentanol OH diethyl ether 4 of 8 ethanol hexane 4 20 pts Nomenclature Name the following molecules using the IUPAC nomenclature a 8 pts CH 3 CH 2 4CHCH2CH 3 CH2CH 3 3 ethyloctance b 8 pts 3 4 diethyl 2 6 dimethylheptane 4 ethyl 5 isopropyl 2 methylheptane c 4 pts Provide the structure of trans 1 3 dimethylcyclopentane H 3C H or H or CH 3 2 pts if the trans relationship of the two methyl groups are not clearly shown 5 of 8 5 26 pts Conformations of alkanes a Following is a planar hexagon representation for one isomer of 1 2 4 trimethylcyclohexane Draw the two chair conformations of this isomer Neatness counts and if the substituent positions are not clear you will not get full credit 10 pts CH 3 CH 3 H H 3C H H 3C H H CH 3 CH 3 CH 3 CH 3 H H H H CH 3 H b In part a above circle the more stable chair conformation For full credit what makes this chair more stable than the other 4 pts It has two of the three methyl in equatorial positions and thus has less 1 3 diaxial interaction than the other chair conformation c Among the following structures CIRCLE the one representing a cis isomer 4 pts CH 3 CH 3 CH 3 CH 3 CH 3 B A C CH 3 d The following potential energy diagrams were obtained from the 360o rotation around the single bonds indicated by arrow in compounds A and B Assign each compound to its potential energy diagram Draw Newman projection corresponding to the most stable conformer of A and assign it to the minimum of the energy diagram 8 pts CH 3 3CCH2 CH 3CH2 CH2C CH 3 3 CH2CH 3 B A Compound A right diagram 4 pts Compound B left diagram C CH 3 3 H H H H 4 pts 10 C CH 3 3 Energy kcal mol Energy kcal mol 6 3 0 5 0 torsion angle torsion angle 6 of 8 6 Acids and bases 24 pts a Rank the following species in order of increasing acidity from 1 to 5 1 least acidic 5 most acidic 6 pts Ranking HF H2 O HCl NH3 3 4 2 5 1 CH3COOH 4 3 Note Please see me if you ranked HF and acetic acid 3 4 or 4 3 Both answers will be accepted b Indicate the acid base conjugate acid and conjugate base in the following acid base reaction Predict whether the equilibrium will favor the reactants left or the products right 10 pts H 2O Clacid base HO conjugate acid HCl conjugate base 2 pts each The equilibrium will favor the reactants left 2 pts c Water H2O can act as an acid or a base 4 pts each 8 pts i When water acts as an acid draw the Lewis structure of its conjugate base H O ii When water acts as a base draw the Lewis structure of its conjugate acid H H O H 7 of 8