California State Polytechnic University, Pomona 1

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1 alifrnia State Plytechnic University, Pmna hem 200 Final Fall, 208 Beauchamp ame Key Prblems Pints redit. Functinal Grup menclature ( large structure) structure and resnance mbustin eactins, alculate cmbustin, using f t cmpare kcal/gram Predict rder f reactivity eactins page (30) S /E 3 chanisms, with all f the details, Templates Prvided Acid / Base hemistry () Free adical mechanism,, types f stereismers yclhexane nfrmatins, 2 substituents, ewman Prj, el. Energies hain nfrmatins, ewman Prj, el. Energies Synthesis prblem () 30. Fill in all mechanistic details, curved arrws, lne pairs, frmal charge, arbcatin earrangements 5 Ttal 285 verall average = Exam average with 00% W = Final Exam pints if 00% = 200 pints: A 85% 80% 70 B 70% 60% 40 B- 68% 57% 36 55% 40% 0-50% 33% 00 40% 20% pints is a guess fr the 00% scre, prbably clse t what it actually will be. It culd be a little less r a little mre. It merely gives yu a number t sht fr as yu cnsider what grade yu are hping t get. This is a lng exam. It has been designed s that n ne questin will make r break yu. The best strategy is t wrk steadily, starting with thse prblems yu understand best. Make sure yu shw all f yur wrk. raw in any lne pairs f electrns, frmal charge and curved arrws t shw electrn mvement where apprpriate. yur best t shw me what yu knw in the time available. The ppsite f a crrect statement is a false statement. But the ppsite f a prfund truth may well be anther prfund truth. iels Bhr

2 alifrnia State Plytechnic University, Pmna 2. Prvide an acceptable name fr the fllwing structure. Indicate the abslute cnfiguratin f any chiral centers shwn in three dimensinal frm (/S) and any E/Z steregenic centers. (30 pts) E S S l 2 5E (,3S) -phenyl-2-benzyl-3-amin-4-amid-5-chlrcarbnyl-9-mercapt-0-(3-heptylcyclbutyl)undec-7-ynyl (2,5E,9Z) 2-hydrxy-3,2-dix-5-(3-methxycarbnyl-7-pentylcyclnn-2E-enyl)-6-(-methylprpxy)- 9-frmyl--cyanddeca-5,0-dienate 9 0 9Z 2. raw tw additinal better 2 resnance structures f the given structure. Assume all nnhydrgen atms have full ctets unless + is written next t carbn. Add in any necessary lne pairs and use prper curved arrws t shw electrn mvement. Which structure(s) is(are) best and why? raw a 3 structure fr the given resnance structure. Shw bnds in frnt f the page as wedges, bnds in back f the page as dashed lines and bnds in the page as simple lines. Shw rbitals fr pi bnds and lne pairs alng with their electrns. (20 pts) K = negative n carbn Best = negative n xygen Best = negative n xygen (6 pts) (4 pts)

3 alifrnia State Plytechnic University, Pmna 3 3. Given the fllwing heats f frmatin ( f ), calculate the energy f cmbustin in kcal per gram fr ethane and ethylene glycl (ethan-,2-dil). Which cmpund has mre energy available per gram? Explain why they are s different. (20 pts) f (ethane) = -20 kcal/mle f (ethylene glycl) = -0 kcal/mle f ( 2 ) = -94 kcal/mle f ( 2 ) = -57 kcal/mle f ( 2 ) = 0 kcal/mle MW ( 3 3 ) = 30 grams/mle MW ( 2 2 ) = 62 grams/mle ef = 0 frmatin cmbustin cmb ( 3 3 ) = 2 x f ( 2 ) + 3 x f ( 2 ) - x f (ethane) x f ( 2 ) cmb ( 3 3 ) = (-88) + (-7) - (-20) - (0) = (-359) - (-20) = -339 kcal/mle cmb ( 2 2 ) = 2 x f ( 2 ) + 3 x f ( 2 ) - x f (ethane) x f ( 2 ) cmb ( 2 2 ) = (-88) + (-7) - (-0) - (0) = (-359) - (-0) = -249 kcal/mle energy gram energy gram (ethane) = (-339 kcal/mle) / 30 grams = -.3 kcal / gram (ethylene glycl) = (-249 kcal/mle) / 62 grams = -4.0 kcal / gram hane has mre energy per gram because there are n bnds t xygen. When hydrgen r carbn bnds t xygen it becmes mre stable (lwer ptential energy) and there is less energy available t generate with new bnds t xygen. hane apprximates a fat and ethylene glycl apprximates a carbhydrate (like glucse). 4. Predict the relative rder f reactivity f the indicated carbnyl cmpunds in reactins with nuclephiles ( = mst reactive carbnyl electrphile). Use all three lgic arguments f rganic chemistry (resnance, inductive and steric). Shw structures, lne pairs and arrw-pushing cnventins in yur answer t prvide an explanatin fr yur rder f reactivity. Write the expected prduct in a reactin with lithium aluminium deuteride, LiAl 4, fllwed by wrkup (n mechanisms). (20 pts) A = middle reactive B 3 3 = least reactive resnance 3 resnance 3 3. LiAl 4 2. wrkup resnance. LiAl 4 2. wrkup 3 3 = mst reactive resnance mpund B (ester) has an extra resnance structure that mves the psitive charge ff f the carbn atm. Since this charge attracts the negative nuclephile we expect the ester t be less reactive. S cmpund A and are mre reactive electrphiles. The difference between A and is " versus " at the electrphilic carbn atm. is mre inductively dnating than and shuld reduce the partial psitive (less reactive) and is larger than which shuld sterically inhibit frmatin f the sp 3 prduct because sp 3 has smaller bnd angles than sp 2, and is mre crwded (therefre the ketne is less reactive). Aldehyde is mre reactive than A (ketne) The verall rder f reactivity is: (aldehyde) > A (ketne) > B (ester) LiAl 4 2. wrkup (2 times) 3

4 alifrnia State Plytechnic University, Pmna 4 5. Fill in the missing prduct r reagent, as needed, fr each reactin belw. nt waste time by writing mechanisms r thinking t much n any ne part. (30 pts) a. a, h a b. c. 3. Mg wk. Li 2. Pl 3. Mg 2. wrkup l 2. p = 5, (- 2 ) 2 2. ab 4 3. wrkup d. r 3 pyridine Li.. LiAl 4 2. wk 2. e. S n-buli. 3 Mg 3 2. wk P 3 f.. Mg wrkup r 3 2. a 2. g. 2 /h. a. a a h.. Mg wrkup. a 3. Tsl/pyridine 2. LiAl 4 2. a 3. wk 2 i. r Mg 2 S 4 2. wrkup j. as S l 3 S Li. 2. S

5 alifrnia State Plytechnic University, Pmna 5 6. Use (2S,3,4)-2-deuteri-3-brm-4-methylhexane t prvide a simple, arrw-pushing mechanism fr each f the fllwing reactin cnditins (shw curved arrws, lne pairs & frmal charge). Fill in the necessary details t clearly indicate any sterechemical features and/r cnfrmatinal requirements. If reactants are nt drawn in the prper rientatin t shw hw the reactin must prceed, then redraw them in a mre infrmative way that shws this. nt cnsider carbcatin rearrangement pssibilities. (40 pts) a. raw a 2 structure and then a 3 structure f the reacting mlecule. A 3 structure will be prvided fr the cst f the pints f this part. (3 pts) 3 2 * * 3 2 structure * = chiral center * structure f (2S,3,4)-2-deuteri-3-brm-4-methylhexane b. Shw a mechanism fr each psitin and simply draw all ther pssible E reactin prducts (what kind?). Indicate if E, Z r neither. Yu can abbreviate cmmn branch names if they are nt part f yur mechanism There may r may nt be fewer prducts than there are numbers. (0 pts) + + ther pssible E prducts 2E alkene with nly three E2 prducts. - 2Z alkene withut 3E alkene E2 mechanism E E / Z cnfiguratin E E / Z cnfiguratin c. Shw the S reactin (what kind?), indicate the abslute cnfiguratin(s) f the center in the prduct. (6 pts) + 4S 4 S 2 mechanism cnfiguratin

6 alifrnia State Plytechnic University, Pmna 6 d. Shw all steps f the S reactin (what kind?). Yu can use ne intermediate t shw all pssible S pssibilities. Indicate the abslute cnfiguratin(s) f the center in the prduct. Yu can abbreviate cmmn branch names if they are nt part f yur mechanism (9 pts) a 2 b - 2 S + S carbcatin mechanism E S e. Shw a mechanism fr tw E prducts and simply draw all ther pssible E reactin prducts (yu can use the same intermediate fr yur tw mechanisms). Indicate if E, Z r neither. There may r may nt be fewer prducts than numbers. (2 pts) 2 a a E + related alkenes a Z shw tw 2 b related alkene b b E b c here are 2 mre (extra) b d d c c mechanism 2 2 Pr Z E E Z

7 alifrnia State Plytechnic University, Pmna 7 7. Shw hw the tw cmpunds shwn react in an acid / base reactin. Include all mechanism details (curved arrws, lne pairs and frmal charge). The acid n the left side has a pk a f and the acid n the right side has a pk a f 0. ecide which prtn is mst acidic n the left side and therefre reactant is the base. That will allw yu t write the crrect cnjugate prducts. Explain why the prtn yu used is the mst acidic prtn. alculate an equilibrium cnstant, K eq fr the reactin. (20 pts) K eq = pk a = K a (left) K a (right) = = 0-2 equilibrium lies t the left Three resnance structure, tw with the negative charge n xygen make this the mst stable cnjugate base, which determines which prtn is mst acidic. pk a = 9 8. Write a mechanism t shw the expected prducts fr the reactin shwn. alculate a fr each step f yur mechanism and the verall reactin. w many stereismers are pssible? What srts f stereismer pssibilities are there? Yu dn t have t write ut any 3 structures, but use s and S s t indicated the types f stereismer pssibilities. (20 pts) 3 h (catalyst) 3 * * * = chiral centers Imprtant bnd energies. - = 40 kcal/mle = 0 kcal/mle - = 88 kcal/mle pi = 64 kcal/mle -() = 95 kcal/mle - = 68kcal/mle. Initiatin 2a. Prpagatin 3 = +64 = -68 2b. Prpagatin 2 = +88 = = +88 = Terminatin - cmbinatin f 2 radicals = 40 kcal/mle = -22 kcal/mle = -4 kcal/mle = -7 kcal/mle = very negative verall = - kcal/mle A 3 B (,2) (S,2S) (S,2) (,2S) enantimers (AB),() diasteremers (A),(A),(B),(B) With 2 chiral centers there are 4 pssible stereismers, 2 pairs f enantimers and 4 pairs f diastermers. Enantimers are ( and SS) and (S and S). iastermers are ( and S), ( and S), (SS and S), (SS and S).

8 alifrnia State Plytechnic University, Pmna 8 9. raw all pssible chair cnfrmatins f cis-- phenyl-2-ethylcyclhexane. Make the left mst ring carbn and number twards the frnt. Shw all axial and equatrial grups in the first chair. raw the mre stable cnfrmatin first. Prvide a reasn fr yur answer. raw a ewman prjectin f the least stable cnfrmatin using the 2 and 4 5 bnds t sight alng. Pint ut any substituent gauche interactins shwn in yur ewman prjectin. The axial energy f an phenyl grup is 2.8 kcal/mle and the axial energy f an ethyl grup is.8 kcal/mle and a phenyl/ethyl gauche interactin is.5 kcal/mle, what is the rati f the tw cnfrmatins at equilibrium? Shw yur wrk. (20 pts) a. K = 0 2.3T = 2 cal/ml-k T = 300 K axial ethyl =.8 gauche = +.5 ttal = chair 2 chair (less stable) (mre stable) cis--phenyl-2-ethylcyclhexane ttal = 3.3 kcal/mle ttal = 4.3 kcal/mle ) = =.0 kcal/mle axial phenyl = +2.8 gauche = +.5 ttal = 4.3 Axial phenyl is higher energy in right structure s is psitive (by.0) and K eq <. b. ewman prjectin ( 2 and 4 5 ) least stable, pint ut any gauche interactins with the substituent(s) 6 h 2 chair 2 (less stable) axial phenyl = +2.8 gauche =.5 ttal = 4.3 gauche 0. Prpse a reasnable synthesis fr the fllwing mlecule. Yu must use the given starting materials and any reagents we have studied in ur curse. (30 pts) Given: 4 a 2 r 3 pyridine. Mg wrkup given. nbuli 2.. Mg wrkup 3 S 3 2 h S given There are many ways t make the target mlecule (TM). Yu culd use a nitrile and Grignard r ketne enlate with chemistry r ther appraches. A cuple f cmbinatins are shwn belw. r 3 pyridine 3 a 3 2 h 4 given

9 alifrnia State Plytechnic University, Pmna 9. Prvide all missing arrw-pushing mechanistic details (curved arrws, lne pairs and frmal charge) t explain the fllwing transfrmatin. Assume all nnhydrgen atms have full ctets unless a psitive charge is written by a carbn atm. (20 pts) a. 3 3 resnance 3 3. wrkup resnance 2. Fill in the missing details t shw hw these 5 steps frm lansterl (nly a partial structure is shwn), which cntinues n t chlesterl in 9 additinal steps. (5 pts) carbcatin rearrangements and a final E reactin. 3 3 B E The bstacle is the path. Zen Prverb

10 alifrnia State Plytechnic University, Pmna 0