Spectropscopy*involves*measurements*of*interac3on*between*light*energy*and*ma9er.**We*focus*on*C*and*H,*because*these*are*the*elements*found*in*all*organic*compounds.*

1*

A*magne3c*moment*creates*a*magne3c*field.*

2*

3*

If*the*total*number*of*protons*and*neutrons*is*even,*then*the*atom*will*not*have*a*magne3c*moment*at*all,*and*it*will*not*be*affected*by*the*external*magne3c*field.*

4*

It*is*more*stable*for*the*nucleus*to*align*with*the*magne3c*field.*

5* 6*

When*the*magne3c*field*strength*is*less,*(because*it*has*been*canceled*or*reduced*by*the*magne3c*field*of*the*circula3ng*electrons)*there*is*a*smaller*energy*gap*

7*

The*structure*that*the*molecule*is*connected*with*determines*the*electronic*environment*for*each*atom*and*thus*what*energy*gap*will*be*observed*for*each*atom*in*the*magne3c*field.**So,*if*certain*energy*gaps*are*observed,*conclusions*can*be*made*about*the*structure*of*the*molecule.*

8*

9* 10*

11*

Deuterated*solvents*are*necessary,*because*a*solvent*with*any*number*of*protons*being*in*large*excess*would*give*a*huge*signal.**Signals*for*the*solute*in*comparison*would*be*indis3nguishable*above*the*noise*in*the*signal.*

12*

13* 14*

15* 16*

17*

Because*of*the*chiral*center*that*the*OH*group*is*a9ached*to,*if*one*of*the*labeled*H*is*replaced*with*a*D*and*then*the*other*labeled*H*atom*is*replaced*with*a*D,*the*resul3ng*compounds*will*be*diastereomers.**Resul3ng*diastereomers*shown*above*

18*

19* 20*

21*

Axial*and*equitorial*protons*have*different*electronic*environments.**If*the*chair*were*not*interconver3ng,*two*signals*would*be*observed.*

22*

If*the*temperature*were*lowered,*and*the*interconversion*were*slowed*down,*then*two*signals*would*be*observed.*

23* 24*

25* 26*

27* 28*

Electronega3ve*atoms*a9ract*electrons*away*from*the*H*atoms*through*induc3on.**With*fewer*electrons*around*the*h*atom,*the*external*magne3c*field*affects*the*H*atom*more*causing*a*larger*energy*gap*between*alpha*and*beta*spin*states.**That*means*a*greater*energy*will*be*necessary*to*put*the*H*atom*in*resonance,*and*the*signal*will*appear*on*the*high*energy*or*downfield*side*of*the*spectra.*

29* 30*

31* 32*

33* 34*

Some*regions*are*more*shielded*than*others,*because*the*electron*density*around*that*area*is*greater,*can*be*affected*by*the*shapes*of*orbitals*and*by*the*presence*of*pi*bonds*versus*sigma*bonds,*and*the*proximity*to*electronega3ve*atoms.*

35*

The*nonequivalent*H*atoms*on*the*ring*(should*see*three*signals)*are*shiWed*to*very*similar*posi3ons,*so*they*overlap*crea3ng*a*signal*that*appears*as*if*it*is*one*signal.*

36*

The*H*atoms*on*the*outside*of*the*structure*appear*at*8*ppm,*while*the*protons*poin3ng*into*the*pi*cloud*appear*around*X1*ppm.*

37* 38*

39* 40*

41*

TertXbutyl*methyl*ether*would*give*two*signals.**One*signal*for*the*methyl*group*at*approximately*3.5*ppm*with*an*integra3on*of*3.**The*other*signal*for*the*tertXbutyl*group,*which*has*three*equivalent*methyl*groups.**Its*shiW*would*be*approximately*1*ppm*with*an*integra3on*of*9.*3Xpentanone*would*have*two*signals*because*of*symmetry.**One*signal*for*the*two*CH2*groups*on*either*side*of*the*carbonyl*with*a*shiW*of*approximately*2.2*ppm*and*an*integra3on*of*4.**The*other*signal*would*shiW*to*approximately*1*ppm*with*an*integra3on*of*6.*

42*

43* 44*

45* 46*

When*one*neighboring*proton*is*shielding*and*the*other*is*deshielding,*the*effects*cancel*out.*

47*

The*triplet*results*when*one*neighboring*proton*shields*and*the*other*deshields*half*the*3me*(giving*the*center*peak*with*a*integra3on*twice*that*of*the*outer*peaks).*

48*

Neighboring*H*atoms*that*align*their*spin*with*the*magne3c*field*have*different*shielding*effects*than*neighboring*H*atoms*that*align*against*the*magne3c*field.*

49*

Integra3on*ra3os*should*be*1:3:3:1*

50*

51*

N+1*rule*means*the*spli]ng*should*be*equal*to*the*number*of*H*atoms*on*the*adjacent*carbon*+1.**Explained*more*through*examples*on*subsequent*slides.*

52*

1,2Xdichloroethane*should*be*a*singlet*

53* 54*

55* 56*

57* 58*

59* 60*

61*

If*nonequivalent*H*atoms*split*with*the*same*coupling*constant,*then*they*act*as*if*they*are*equivalent,*and*the*spli]ng*pa9ern*will*follow*the*n+1*rule.**See*analysis*for*(S)XpentX2XenX4Xol*on*following*slide.*

62*

If*nonequivalent*H*atoms*split*with*the*same*coupling*constant,*then*they*act*as*if*they*are*equivalent,*and*the*spli]ng*pa9ern*will*follow*the*n+1*rule.**See*analysis*for*(S)XpentX2XenX4Xol*on*following*slide.*

63* 64*

Mechanism*on*next*slide*

65* 66*

The*solvent*will*be*in*a*large*excess,*so*the*equilibrium*created*where*some3mes*the*molecule*has*a*H*atom*and*some3mes*a*D*atom*will*favor*replacement*of*the*H*atom*with*D*atoms.*

67* 68*

Each*molecule*has*similar*func3onal*groups,*so*the*stretching*vibra3ons*will*be*very*similar*prac3cally*indis3nguishable.**The*proton*NMR*for*each*would*give*a*different*number*of*signals*(from*leW*to*right*3*signals,*4*signals,*2*signals).*

69*

The*right*hand*side*of*the*molecule*is*the*same*for*both,*but*on*the*leW*hand*side*other*the*molecule,*the*spli]ng*pa9ers*will*be*different.**Moving*from*leW*to*right,*the*molecule*on*the*leW*has*a*doublet,*quartet,*singlet,*etc.**The*molecule*on*the*right*has*a*triplet,*quartet,*singlet,*etc.*

70*

71*

HDI*=*1.**The*singlet*integra3ng*to*6H*suggests*two*methyl*groups.*

72*

The*doublet*of*quartets*shiWed*to*5.3*ppm*suggests*a*CH*a9ached*to*a*C=C*double*bond*with*a*methyl*group*a9ached*to*the*carbon*and*a*single*H*on*the*other*carbon*of*the*C=C*double*bond.**The*peak*at*3.4*ppm*suggests*that*there*is*a*carbon*with*2*H*atoms*a9ached*to*the*Cl*and*next*to*a*carbon*with*no*H*atoms*on*it.**The*molecule*works*out*to*be*cis*or*trans*5XchloroX4,4XdimethylX2Xpentene.*

73* 74*

75* 76*

2*signals*

77* 78*

79* 80*

81*

In*the*molecule*on*the*leW,*the*CH2*is*shiWed*farthest*downfield.**In*the*molecule*on*the*right,*the*CH*is*shiWed*farthest*downfield,*and*in*DEPT*CH*and*CH2*are*dis3nguishable.*

82*

Some*3ssues*have*more*water*versus*other*molecules*that*may*have*more*carbon*or*other*elements.**A*3D*image*results*from*the*different*signals*given*in*different*3ssues.**No*known*side*effects*to*radio*waves*or*magne3c*fields.*

83*