CEM1611 Answers to Prolem Sheet 9 1. Tutomers re struturl isomers whih re relte y migrtion of hyrogen tom n the exhnge of single on n jent oule on. Compoun Tutomer 2 2 2 2 2 2 2 2 2 2 2
2. () Whih pir (or pirs) re onstitutionl isomers? () n (e) () () () Whih pir (or pirs) re istereoisomers? () Whih pir (or pirs) re enntiomers? () Whih pir (or pirs) re (E)- / (Z)-isomers? () () C 3 C 3 n C 3 C 3 Both ompouns re C 4 8 ut iffer in the nture n sequene of oning, hene onstitutionl isomers. () C 3 C 2 C 3 n C 3 C 2 C 3 Sme nture n sequene of oning n not simply onformtions of the sme ompoun thus these ompouns re onfigurtionl isomers. Interonversion of the two ompouns n only e hieve y reking one of the ons n reforming the moleule in the opposite onfigurtion. on-superimposle mirror imges, hene enntiomers.
() C C n C C Sme nture n sequene of oning n not simply onformtions of the sme ompoun thus these ompouns re onfigurtionl isomers. Interonversion of the two ompouns n only e hieve y reking the oule on n reforming it in the opposite onfigurtion. These re (E)/(Z)-isomers, suset of the onfigurtionl isomers lss: istereoisomers (non-superimposle, not mirror-imge relte). () C 3 C n C 3 C These re the sme ompoun. Rottion of the first ntilokwise, roun the C-C on. (e) n Both C 5 7 ut the ompouns iffer in the nture n sequene of oning, hene onstitutionl isomers. 3. hirl - plne of symmetry pssing through entre of C=C n C group
Informtion for nswering questions 4 n 5: The sequene rules for ssigning priorities to sustituents on stereogeni entre re: (i) Look t the four toms iretly tthe to the stereogeni entre n ssign priorities in orer of eresing tomi numer. (ii) If eision out priority n not e rehe y pplying rule 1, ompre tomi numers of the seon toms of eh sustituent, ontinuing outwrs if neessry until the first point of ifferene is rehe. (iii) Multiple-one toms re onsiere s n equivlent numer of single one toms. 4. After ssigning priorities to the groups on eh en of the C=C on s ove, the struture is then viewe with the sustituent with the lowest priority projeting kwrs. If urve rrow rwn from the highest to seon-highest to thir-highest priority sustituent is lokwise, the onfigurtion is (R). If the urve rrow is ntilokwise, the onfigurtion is (S). 3 C C 2 C 3 C C 3 - - is ntilokwise: S = C 2 C 3 nee to reorientte with t the k C 3 CF 3 nee to reorientte with t the k = - - is lokwise: R 3 C C 2 - - is lokwise: R C 3 CF 3 - - is ntilokwise: S
3 C C 3 = 3 C C 3 nee to reorientte with t the k - - is lokwise: R - - is lokwise: R 5. After ssigning priorities to the groups on eh en of the C=C on s ove, the rrngement is Z if oth the sustituents of higher priority re on the sme sie n E if they re on opposite sies. C C 3 2 C 3 C C 3 3 C C 3 3 C C E Z E 5. () The strting mteril is hirl n the retion gives rise to the genertion of hirl ron. Both fes of the lkene oule on re eqully essile to the 2 n hene ompoun (F) is otine s the remi mixture. () The priorities of the sustituents on the hirl ron in F re: > C 2 > C 2 C 3 > The (R) enntiomer hs the onfigurtion shown elow in orer to get lokwise rrow from C 2 C 3 C 3 with the ple t the k: 3 C 2 C C 2 - - is lokwise: R