. Spetrosopy Mss spetrosopy igh resolution mss spetrometry n e used to determine the moleulr formul of ompound from the urte mss of the moleulr ion For exmple, the following moleulr formuls ll hve rough M r of 60, ut more preise M r n give the moleulr formul. e.g. M r = 60.0 moleulr formul = 4 M r M r = 60.0575 moleulr formul = 8 = 60.05 moleulr formul = 4 N igh resolution mss spetrosopy n mesure the mss to 5 d.p. This n help differentite etween ompounds tht pper to hve similr Mr (to the nerest whole numer) Aurte msses of toms: =.0078 =.0000 = 5.9949 N = 4.00 Exmple A ompound is found to hve n urte reltive formul mss of 46.047. It is thought to e either or N N. lulte the M r of eh ompound to 4 deiml ples to work out whih one it is. = (.0000 x ) + (5.9949 x ) + (.0078 x6) = 46.047 N N. = (.0000 x ) + (4.00 x ) + (.0078 x6) = 46.050 Frgmenttion When orgni moleules re pssed through mss spetrometer, it detets oth the whole moleule nd frgments of the moleule. Moleulr ion formed: M [M] +. + e The moleule loses n eletron nd eomes oth n ion nd free rdil Severl peks in the mss spetrum our due to frgmenttion. The Moleulr ion frgments due to ovlent onds reking: [M] +. X + + Y. Reltively stle ions suh s rotions R + suh s + nd ylium ions [R-=] + re ommon. The more stle the ion, the greter the pek intensity. The pek with the highest mss/hrge rtio will e normlly due to the originl moleule tht hsn t frgmented (lled the moleulr ion). As the hrge of the ion is + the mss/ hrge rtio is equl to Mr. This proess produes n ion nd free rdil. The ion is responsile for the pek The yl group present in ronyls, esters id derivtives is R ommon stle ion + Mss spetrum for utne 9 4 4 0 = 58 Eqution for formtion moleulr ion 4 0 [ 4 0 ] +. + e m/z 58 Equtions for formtion of frgment ions from moleulr ions [ 4 0 ] +. [ ] + +. m/z 4 [ 4 0 ] +. [ ] + +. m/z 9 Mss spetrum for utnone The high pek t 4 due to stility of yl group 4 [ ] + Eqution for formtion moleulr ion [ ] +. + e m/z 7 Equtions for formtion of frgment ions from moleulr ions [ ] +. [ ] + +. m/z 57 9 [ ] + [ ] + 57 [ ] +. 7 [ ] +. [ ] + +. m/z 4 [ ] +. [ ] + +. m/z 9 N Goly hemrevise.org
Infrred spetrosopy ertin groups in moleule sor infr-red rdition t hrteristi frequenies omplited spetr n e otined thn provide informtion out the types of onds present in moleule ABVE 500 m - Funtionl group identifition BELW 500 m - Fingerprinting omplited nd ontins mny signls piking out funtionl group signls diffiult. This prt of the spetrum is unique for every ompound, nd so n e used s "fingerprint". e.g. = 680 750 m - - (id) 500-000 m - Use n IR sorption tle provided in exm to dedue presene or sene of prtiulr onds or funtionl groups A omputer will ompre the IR spetr ginst dtse of known pure ompounds to identify the ompound use spetr to identify prtiulr funtionl groups nd to identify impurities, limited to dt presented in wvenumer form Spetr for utnl 000 500 = Asorption or trough in etween 680-750 m - rnge indites presene of = ond Alwys quote the wve numer rnge from the dt sheet - sorptions tend to e rod Asorption or trough in etween 500-000 m - rnge indites presene of - ond in n id Spetr for ethnoi id = rogue sorptions n lso our nd re inditors of impurities N Goly hemrevise.org
NMR spetrosopy Different types of NMR There re two min types of NMR. NMR. (proton) NMR There is only round % in orgni moleules ut modern NMR mhines re sensitive enough to give full spetr for The spetr is simpler spetrum thn the NMR Equivlent ron toms. In NMR spetrum, there is one signl (pek) for eh set of equivlent toms. d peks 4 peks, dinitroenzene, dinitroenzene,4 dinitroenzene N peks N 4 peks peks d 4 peks peks l d peks d e N 5 peks Equivlent ydrogen toms. In n NMR spetrum, there is one signl for eh set of equivlent toms. Ethnol hs groups of different hydrogen toms sets of equivlent s: rtio ::9 sets of equivlent s: rtio :: In ddition the intensity (integrtion vlue) of eh signl is proportionl to the numer of equivlent toms it represents. Br d d d 4sets of equivlent s: rtio 6::: signl sets of equivlent s: rtio :: 4 sets of equivlent s: rtio ::: d N Goly hemrevise.org
Solvents Smples re dissolved in solvents without ny toms, e.g. l 4, Dl. This mens tht in the NMR the solvent will not give ny peks The sme solvent is used in NMR nd in this se there will e one pek due to the solvent tht will pper on the spetrum. owever, it is known where this pek is so it n e ignored. In the exm it is likely this pek will not our on the spetr. lirtion nd shift A smll mount of TMS (tetrmethylsilne) is dded to the smple to lirte the spetrum TMS is used euse: its signl is wy from ll the others it only gives one signl it is non-toxi it is inert it hs low oiling point nd so n e removed from smple esily Si tetrmethylsilne The sme lirtion ompound is used for oth nd NMR The spetr re reorded on sle known s the hemil shift (δ), whih is how muh the field hs shifted wy from the field for TMS.. The δ is mesure in prts per million (ppm) is reltive sle of how fr the frequeny of the proton signl hs shifted wy from tht for TMS. 0 9 8 7 6 5 4 δ hemil shift (ppm) 0 NMR shift The δ depends on wht other toms/groups re ner the more eletronegtive groups gives greter shift. δ ppm N Goly hemrevise.org δ ppm 4
NMR shift 50-90 5-40 60-85 0-40 Spin-Spin oupling in Nmr In high resolution NMR eh signl in the spetrum n e split into further lines due to inequivlent s on neighouring toms. ppm Nulei in identil hemil environments do not show oupling mongst themselves! Splitting of pek = numer of inequivlent s on neighouring toms + signl singlet doulet triplet qurtet pperne Split numer of peks numer of neighouring inequivlent toms 4 0 reltive size : :: ::: The pek due to group will e triplet s it is next to ( ron with s) The pek due to group will e qurtet s it is next to ( ron with s) The pek due to group will e singlet s it is next to ron with no s) The pek due to group will e triplet s it is next to ron with s Shift 0.7-. Integrtion tre The pek due to group will e singlet s it is next to ron with 0 s Shift.-.6 Integrtion tre The pek due to group will e qurtet s it is next to ron with s Shift.7-4. Integrtion tre ppm N Goly hemrevise.org 5
hromtogrphy hromtogrphy is n nlytil tehnique tht seprtes omponents in mixture etween moile phse nd sttionry phse. Seprtion y olumn hromtogrphy depends on the lne etween soluility in the moving phse nd retention in the sttionry phse. A solid sttionry phse seprtes y dsorption, A liquid sttionry phse seprtes y reltive soluility The moile phse my e liquid or gs. The sttionry phse my e solid (s in thinlyer hromtogrphy, TL) or either liquid or solid on solid support (s in gs hromtogrphy, G) If the sttionry phse ws polr nd the moving phse ws non- polr e.g. exne. Then nonpolr ompounds would pss through the olumn more quikly thn polr ompounds s they would hve greter soluility in the non-polr moving phse. (Think out intermoleulr fores) PL stnds for high performne liquid hromtogrphy. PL: sttionry phse is solid sili PL: moile phse liquid In gs-liquid hromtogrphy G the moile phse is inert gs suh s nitrogen, helium, rgon. The Sttionry phse is liquid on n inert solid. Gs-Liquid hromtogrphy Gs-liquid hromtogrphy n e used to seprte mixtures of voltile liquids. The time tken for prtiulr ompound to trvel from the injetion of the smple to where it leves the olumn to the detetor is known s its retention time. This n e used to identify sustne. Flow ontrol In gs-liquid hromtogrphy, the moile phse is gs suh s helium nd the sttionry phse is high oiling point liquid sored onto solid. Smple in oven Some ompounds hve similr retention times so will not e distinguished. disply Bsi gs-liquid hromtogrphy will tell us how mny omponents there re in the mixture y the numer of peks. It will lso tell us the undne of eh sustne. The re under eh pek will e proportionl to the undne of tht omponent. rrier gs olumn detetor Wste outlet It is lso possile for gs-liquid hromtogrphy mhine to e onneted to mss spetrometer, IR or NMR mhine, enling ll the omponents in mixture to e identified. G-MS is used in nlysis, in forensis, environmentl nlysis, irport seurity nd spe proes. Most ommonly mss spetrometer is omined with G to generte mss spetr whih n e nlysed or ompred with spetrl dtse y omputer for positive identifition of eh omponent in the mixture. N Goly hemrevise.org 6
Bringing it ll together. Work out empiril formul Elementl nlysis 66.6%.8%.9%. Using moleulr ion pek m/z vlue from mss spetrum lulte Moleulr formul moleulr ion pek m/z vlue= 44 66.6/.8/.9/6 =5.555 =.8 =.86875 =4 =8 = Mr empiril formul 4 8 = 7 If Mr moleulr formul 44 then ompound is 8 6. Use IR spetr to identify min onds/funtionl group 8 6 ould e n ester, roxyli id or omintion of lohol nd ronyl. Look for IR spetr for = nd - onds There is = ut no - sorptions, so must e n ester. - = 4. Use NMR spetr to give detils of ron hin 4 peks only 4 different environments. singlet of re 9 At δ =0.9 Mens groups 9 Pek t δ 4 shows Are suggests Qurtet mens next to Pek t δ. shows = Are suggests Singlet mens djent to with no hydrogens Pek t δ. shows R- Are mens Triplet mens next to 5 4 δ ppm Put ll together to give finl struture N Goly hemrevise.org 7