NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities Hugo E.Gottlieb,*Vadim Kotlyar,and
Abraham Nudelman*
四级试题
Department of Chemistry,Bar-Ilan University,
Ramat-Gan52900,Israel
Received June27,1997
In the cour of the routine u of NMR as an aid for organic chemistry,a day-to-day problem is the identifica-tion of signals deriving from common contaminants (water,solvents,stabilizers,oils)in less-than-analyti-cally-pure samples.This data may be available in the literature,but the time involved in arching for it may be considerable.Another issue is the concentration dependence of chemical shifts(especially1H);results obtained two or three decades ago usually refer to much more concentrated samples,and run at lower magnetic fields,than today’s practice.
We therefore decided to collect1H and13C chemical shifts of what are,in our experience,the most popular “extra peaks”in a variety of commonly ud NMR solvents,in the hope that this will be of assist
ance to the practicing chemist.
Experimental Section
美しきものNMR spectra were taken in a Bruker DPX-300instrument (300.1and75.5MHz for1H and13C,respectively).Unless otherwi indicated,all were run at room temperature(24(1°C).For the experiments in the last ction of this paper,probe temperatures were measured with a calibrated Eurotherm840/T digital thermometer,connected to a thermocouple which was introduced into an NMR tube filled with mineral oil to ap-proximately the same level as a typical sample.At each temperature,the D2O samples were left to equilibrate for at least 10min before the data were collected.
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In order to avoid having to obtain hundreds of spectra,we prepared ven stock solutions containing approximately equal amounts of veral of our entries,chon in such a way as to prevent intermolecular interactions and possible ambiguities in assignment.Solution1:acetone,tert-butyl methyl ether,di-methylformamide,ethanol,toluene.Solution2:benzene,di-methyl sulfoxide,ethyl acetate,methanol.Solution3:acetic acid,chloroform,diethyl ether,2-propanol,tetrahydrofuran. Solution4:acetonitrile,dichloromethane,dioxane,n-hexane, HMPA.Solution5:1,2-dichloroethane,ethyl
methyl ketone, n-pentane,pyridine.Solution6:tert-butyl alcohol,BHT,cyclo-hexane,1,2-dimethoxyethane,nitromethane,silicone grea, triethylamine.Solution7:diglyme,dimethylacetamide,ethyl-ene glycol,“grea”(engine oil).For D2O.Solution1:acetone, tert-butyl methyl ether,dimethylformamide,ethanol,2-propanol. Solution2:dimethyl sulfoxide,ethyl acetate,ethylene glycol, methanol.Solution3:acetonitrile,diglyme,dioxane,HMPA, pyridine.Solution4:1,2-dimethoxyethane,dimethylacetamide, ethyl methyl ketone,triethylamine.Solution5:acetic acid,tert-butyl alcohol,diethyl ether,tetrahydrofuran.In D2O and CD3OD nitromethane was run parately,as the protons exchanged with deuterium in prence of triethylamine.
Results
Proton Spectra(Table1).A sample of0.6mL of the solvent,containing1µL of TMS,1was first run on its own.From this spectrum we determined the chemical shifts of the solvent residual peak2and the water peak. It should be noted that the latter is quite temperature-dependent(vide infra).Also,any potential hydrogen-bond acceptor will tend to shift the water signal down-field;this is particularly true for nonpolar solvents.In contrast,DMSO the water is already strongly hydrogen-bonded to the solvent,and solutes have only a negligible effect on its chemical shift.This is also true for D2O;the ch
emical shift of the residual HDO is very temperature-dependent(vide infra)but,maybe counter-intuitively,remarkably solute(and pH)independent. We then added3µL of one of our stock solutions to the NMR tube.The chemical shifts were read and are prented in Table 1.Except where indicated,the coupling constants,and therefore the peak shapes,are esntially solvent-independent and are prented only once.
For D2O as a solvent,the accepted reference peak(δ)0)is the methyl signal of the sodium salt of3-(trimeth-ylsilyl)propanesulfonic acid;one crystal of this was added to each NMR tube.This material has veral disadvan-tages,however:it is not volatile,so it cannot be readily eliminated if the sample has to be recovered.In addition, unless one purchas it in the relatively expensive deuterated form,it adds three more signals to the spectrum(methylenes1,2,and3appear at2.91,1.76, and0.63ppm,respectively).We suggest that the re-sidual HDO peak be ud as a condary reference;we find that if the effects of temperature are taken into account(vide infra),this is very reproducible.For D2O, we ud a different t of stock solutions,since many of the less polar substrates are not significantly water-soluble(e Table1).We also ran sodium acetate and sodium formate(chemical shifts: 1.90and8.44ppm, respectively).
Carbon Spectra(Table2).To each tube,50µL of the stock solution and3µL of TMS1were added.The so
lvent chemical shifts3were obtained from the spectra containing the solutes,and the ranges of chemical shifts
(1)For recommendations on the publication of NMR data,e: IUPAC Commission on Molecular Structure and Spectroscopy.Pure Appl.Chem.1972,29,627;1976,45,217.
(,the signal of the proton for the isotopomer with one less deuterium than the perdeuterated ,C H Cl3in CDCl3or C6D5H in C6D6.Except for CHCl3,the splitting due to J HD is typically obrved(to a good approximation,it is1/6.5of the value of the corresponding J HH).For CHD2groups(deuterated acetone,DMSO, acetonitrile),this signal is a1:2:3:2:1quintet with a splitting of ca.2 Hz.
(3)In contrast to what was said in note2,in the13C spectra the solvent signal is due to the perdeuterated isotopomer,and the one-bond couplings to deuterium are always obrvable(ca.20-30Hz). Figure1.Chemical shift of H DO as a function of tempera-ture.
7512J.Org.Chem.1997,62,7512-7515
S0022-3263(97)01176-6CCC:$14.00©1997American Chemical Society
show their degree of variability.Occasionally,in order to distinguish between peaks who assignment was ambiguous,a further1-2µL of a specific substrate were added and the spectra run again.
Table1.1H NMR Data
气体用英语怎么说
proton mult CDCl3(CD3)2CO(CD3)2SO C6D6CD3CN CD3OD D2O solvent residual peak7.26 2.05 2.507.16 1.94 3.31 4.79 H2O s 1.56 2.84a 3.33a0.40 2.13 4.87
acetic acid CH3s 2.10 1.96 1.91 1.55 1.96 1.99 2.08 acetone CH3s 2.17 2.09 2.09 1.55 2.08 2.15 2.22 acetonitrile CH3s 2.10 2.05 2.07 1.55 1.96 2.03 2.06 benzene CH s7.367.367.377.157.377.33
tert-butyl alcohol CH3s 1.28 1.18 1.11 1.05 1.16 1.40 1.24 OH c s 4.19 1.55 2.18
tert-butyl methyl ether CCH3s 1.19 1.13 1.11 1.07 1.14 1.15 1.21 OCH3s 3.22 3.13 3.08 3.04 3.13 3.20 3.22 BHT b ArH s 6.98 6.96 6.877.05 6.97 6.92mogii
OH c s 5.01 6.65 4.79 5.20
ArCH3s 2.27 2.22 2.18 2.24 2.22 2.21
ArC(CH3)3s 1.43 1.41 1.36 1.38 1.39 1.40
chloroform CH s7.268.028.32 6.157.587.90 cyclohexane CH2s 1.43 1.43 1.40 1.40 1.44 1.45
1,2-dichloroethane CH2s 3.73 3.87 3.90 2.90 3.81 3.78 dichloromethane CH2s 5.30 5.63 5.76 4.27 5.44 5.49
diethyl ether CH3t,7 1.21 1.11 1.09 1.11 1.12 1.18 1.17 CH2q,7 3.48 3.41 3.38 3.26 3.42 3.49 3.56 diglyme CH2m 3.65 3.56 3.51 3.46 3.53 3.61 3.67 CH2m 3.57 3.47 3.38 3.34 3.45 3.58 3.61
OCH3s 3.39 3.28 3.24 3.11 3.29 3.35 3.37 1,2-dimethoxyethane CH3s 3.40 3.28 3.24 3.12 3.28 3.35 3.37 CH2s 3.55 3.46 3.43 3.33 3.45 3.52 3.60 dimethylacetamide CH3CO s 2.09 1.97 1.96 1.60 1.97 2.07 2.08 NCH3s 3.02 3.00 2.94 2.57 2.96 3.31 3.06
NCH3s 2.94 2.83 2.78 2.05 2.83 2.92 2.90 dimethylformamide CH s8.027.967.957.637.927.977.92 CH3s 2.96 2.94 2.89 2.36 2.89 2.99 3.01
CH3s 2.88 2.78 2.73 1.86 2.77 2.86 2.85 dimethyl sulfoxide CH3s 2.62 2.52 2.54 1.68 2.50 2.65 2.71 dioxane CH2s 3.71 3.59 3.57 3.35 3.60 3.66 3.75 ethanol CH3t,7 1.25 1.12 1.060.9
6 1.12 1.19 1.17 CH2q,7d 3.72 3.57 3.44 3.34 3.54 3.60 3.65
OH s c,d 1.32 3.39 4.63 2.47
ethyl acetate CH3CO s 2.05 1.97 1.99 1.65 1.97 2.01 2.07
C H2CH3q,7 4.12 4.05 4.03 3.89 4.06 4.09 4.14
职称英语考试报名网CH2C H3t,7 1.26 1.20 1.170.92 1.20 1.24 1.24 ethyl methyl ketone CH3CO s 2.14 2.07 2.07 1.58 2.06 2.12 2.19
C H2CH3q,7 2.46 2.45 2.43 1.81 2.43 2.50 3.18
CH2C H3t,7 1.060.960.910.850.96 1.01 1.26 ethylene glycol CH s e 3.76 3.28 3.34 3.41 3.51 3.59 3.65“grea”f CH3m0.860.870.920.860.88
CH2br s 1.26 1.29 1.36 1.27 1.29
n-hexane CH3t0.880.880.860.890.890.90
CH2m 1.26 1.28 1.25 1.24 1.28 1.29
HMPA g CH3d,9.5 2.65 2.59 2.53 2.40 2.57 2.64 2.61 methanol CH3s h 3.49 3.31 3.16 3.07 3.28 3.34 3.34 OH s c,h 1.09 3.12 4.01 2.16硕士学位英文
nitromethane CH3s 4.33 4.43 4.42 2.94 4.31 4.34 4.40 n-pentane CH3t,70.880.880.860.870.890.90
如何开汽车美容店CH2m 1.27 1.27 1.27 1.23 1.29 1.29
2-propanol CH3d,6 1.22 1.10 1.040.95 1.09 1.50 1.17 CH p,6 4.04 3.90 3.78 3.67 3.87 3.92 4.02 pyridine CH(2)m8.628.588.588.538.578.538.52 CH(3)m7.297.357.39 6.667.337.447.45
CH(4)m7.687.767.79 6.987.737.857.87 silicone grea i CH3s0.070.130.290.080.10 tetrahydrofuran CH2m 1.85 1.79 1.76 1.40 1.80 1.87 1.88 CH2O m 3.76 3.63 3.60 3.57 3.64 3.71 3.74 toluene CH3s 2.36 2.32 2.30 2.11 2.33 2.32
CH(o/p)m7.177.1-7.27.187.027.1-7.37.16
CH(m)m7.257.1-7.27.257.137.1-7.37.16 triethylamine CH3t,7 1.030.960.930.960.96 1.050.99 CH2q,7 2.53 2.45 2.43 2.40 2.45 2.58 2.57
a In the solvents the intermolecular rate of exchange is slow enough that a peak due to HDO is usually also obrved;it appears at
2.81and
3.30ppm in acetone and DMSO,respectively.In the former solvent,it is often en as a1:1:1triplet,with2J H,D)1Hz. b2,6-Dimethyl-4-tert-butylphenol.c The signals from exchangeable protons were not always identified.d In some cas(e note a),the coupling interaction between the CH2and the OH protons may be obrved(J)5Hz).e In CD3CN,the OH proton was en as a multiplet atδ2.69,and extra coupling was also apparent on the methylene peak.f Long-chain,linear aliphatic hydrocarbons.Their solubility in DMSO was too low to give visible peaks.g Hexamethylphosphoramide.h In some cas(e notes a,d),the coupling interaction between the CH3and the OH protons may be obrved(J)5.5Hz).i Poly(dimethylsiloxane).Its solubility in DMSO was too low to give visible peaks.
Notes J.Org.Chem.,Vol.62,No.21,19977513
7514J.Org.Chem.,Vol.62,No.21,1997Notes
Table2.13C NMR Data a
CDCl3(CD3)2CO(CD3)2SO C6D6CD3CN CD3OD D2O solvent signals77.16(0.0629.84(0.0139.52(0.06128.06(0.02 1.32(0.0249.00(0.01
206.26(0.13118.26(0.02
acetic acid CO175.99172.31171.93175.82173.21175.11177.21 CH320.8120.5120.9520.3720.7320.5621.03 acetone CO207.07205.87206.31204.43207.43209.67215.94 CH330.9230.6030.5630.1430.9130.6730.89 acetonitrile CN116.43117.60117.91116.02118.26118.06119.68 CH3 1.89 1.12 1.030.20 1.790.85 1.47 benzene CH128.37129.15128.30128.62129.32129.34
tert-butyl alcohol C69.1568.1366.8868.1968.7469.4070.36 CH331.2530.7230.3830.4730.6830.9130.29 tert-butyl methyl ether OCH349.4549.3548.7049.1949.5249.6649.37 C72.8772.8172.0472.4073.1774.3275.62
C C H326.9927.2426.7927.0927.2827.2226.60 BHT C(1)151.55152.51151.47152.05152.42152.85
C(2)135.87138.19139.12136.08138.13139.09
CH(3)125.55129.05127.97128.52129.61129.49
C(4)128.27126.03124.85125.83126.38126.11
CH3Ar21.2021.3120.9721.4021.2321.38
C H3C30.3331.6131.2531.3431.5031.15
C34.2535.0034.3334.3535.0535.36
chloroform CH77.3679.1979.1677.7979.1779.44
cyclohexane CH226.9427.5126.3327.2327.6327.96
1,2-dichloroethane CH243.5045.2545.0243.5945.5445.11 dichloromethane CH253.5254.9554.8453.4655.3254.78
diethyl ether CH315.2015.7815.1215.4615.6315.4614.77 CH265.9166.1262.0565.9466.3266.8866.42 diglyme CH359.0158.7757.9858.6658.9059.0658.67 CH270.5171.0369.5470.8770.9971.3370.05
CH271.9072.6371.2572.3572.6372.9271.63 1,2-dimethoxyethane CH359.0858.4558.0158.6858.895
9.0658.67 CH271.8472.4717.0772.2172.4772.7271.49 dimethylacetamide CH321.5321.5121.2921.1621.7621.3221.09 CO171.07170.61169.54169.95171.31173.32174.57
NCH335.2834.8937.3834.6735.1735.5035.03
NCH338.1337.9234.4237.0338.2638.4338.76 dimethylformamide CH162.62162.79162.29162.13163.31164.73165.53 CH336.5036.1535.7335.2536.5736.8937.54
CH331.4531.0330.7330.7231.3231.6132.03 dimethyl sulfoxide CH340.7641.2340.4540.0341.3140.4539.39 dioxane CH267.1467.6066.3667.1667.7268.1167.19 ethanol CH318.4118.8918.5118.7218.8018.4017.47 CH258.2857.7256.0757.8657.9658.2658.05 ethyl acetate C H3CO21.0420.8320.6820.5621.1620.8821.15 CO171.36170.96170.31170.44171.68172.89175.26
CH260.4960.5659.7460.2160.9861.5062.32
CH314.1914.5014.4014.1914.5414.4913.92 ethyl methyl ketone C H3CO29.4929.3029.2628.5629.6029.3929.49 CO209.56208.30208.72206.55209.88212.16218.43
C H2CH336.8936.7535.8336.3637.0937.3437.27
CH2C H37.868.037.617.918.148.097.87 ethylene glycol CH263.7964.2662.7664.3464.2264.3063.17“grea”CH229.7630.7329.2030.2130.8631.29
n-hexane CH314.1414.3413.8814.3214.4314.45
CH2(2)22.7023.2822.0523.0423.4023.68
CH2(3)31.6432.3030.9531.9632.3632.73
HMPA b CH336.8737.0436.4236.8837.1037.0036.46 methanol CH350.4149.7748.5949.9749.9049.8649.50c nitromethane CH362.5063.2163.2861.1663.6663.0863.22 n-pentane CH314.0814.2913.2814.2514.3714.39
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CH2(2)22.3822.9821.7022.7223.0823.38
CH2(3)34.1634.8333.4834.4534.8935.30
2-propanol CH325.1425.6725.4325.1825.5525.2724.38 CH64.5063.8564.9264.2364.3064.7164.88 pyridine CH(2)149.90150.67149.58150.27150.76150.07149.18 CH(3)123.75124.57123.84123.58127.76125.53125.12
CH(4)135.96136.56136.05135.28136.89138.35138.27 silicone grea CH3 1.04 1.40 1.38 2.10 tetrahydrofuran CH225.6226.1525.1425.7226.2726.4825.67 CH2O67.9768.0767.0367.8068.3368.8368.68 toluene CH321.4621.4620.9921.1021.5021.50
C(i)137.89138.48137.35137.91138.90138.85
CH(o)129.07129.76128.88129.33129.94129.91
CH(m)128.26129.03128.18128.56129.23129.20
CH(p)125.33126.12125.29125.68126.28126.29
triethylamine CH311.6112.4911.7412.3512.3811.099.07 CH246.2547.0745.7446.7747.1046.9647.19
a See footnotes for Table1.b2J PC)3Hz.c Reference material;e text.
For D2O solutions there is no accepted reference for carbon chemical shifts.We suggest the addition of a drop of methanol,and the position of its signal to be defined as49.50ppm;on this basis,the entries in Table2were recorded.The chemical shifts thus obtained are,on the whole,very similar to tho for the other solvents. Alternatively,we suggest the u of dioxane when the methanol peak is
expected to fall in a crowded area of the spectrum.We also report the chemical shifts of sodium formate(171.67ppm),sodium acetate(182.02and 23.97ppm),sodium carbonate(168.88ppm),sodium bicarbonate(161.08ppm),and sodium3-(trimethylsilyl)-propanesulfonate[54.90,19.66,15.56(methylenes1,2, and3,respectively),and-2.04ppm(methyls)],in D2O. Temperature Dependence of HDO Chemical Shifts.We recorded the1H spectrum of a sample of D2O, containing a crystal of sodium3-(trimethylsilyl)propane-sulfonate as reference,as a function of temperature.The data are shown in Figure1.The solid line connecting the experimental points corresponds to the equation which reproduces the measured values to better than1 ppb.For the0-50o C range,the simpler
gives values correct to10ppb.For both equations,T is the temperature in°C.
Acknowledgment.Generous support for this work by the Minerva Foundation and the Otto Mayerhoff Center for the Study of Drug-Receptor Interactions at Bar-Ilan University is gratefully acknowledged.
JO971176V
δ)5.060-0.0122T+(2.11×10-5)T2(1)
δ)5.051-0.0111T(2)
Notes J.Org.Chem.,Vol.62,No.21,19977515
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