Nmr solvents and impurities

Picos de solventes e impurezas observados no RMN

1. Chem 136 Spring 2003
Handouts

NMR Solvents & Impurities

2. 29 Sample Preparation nd Sample Se

is changed from CDCI, 10 CaDa, whereas dowafici shits are sometimes observed for
CDSCN. The solvent used should always be specified when reporting "chemical shits
‘This is not as important when reporing DC shits, because they vary ony slightly when
the solven is changed from CDCH, to CD. These and other deuterated solvents are
‘commercially availabe in high percetaes (ypicaly greater than 99.9%) of deuterium
enichmest. The small amount of residual hydrogen doesnot usualy obscure regions of
interest in HNMR. A summary ofthe IC and 1H chemical sift fora variety of solvents
relaie to TMS can be found in Table 23. The standard sits shown inthis ble canbe
assigned to solvent peak. so tan be used as an neral chemical sift reference, which
‘would substitue for adding TMS as an interval standard,

"The est way to assess he quality fa spectrum st examine the signa height lative
Lo these andthe shrpnes of peaks, Narrow ln wide ar observed for "Hand canbe
measured by examining be width fs peak ut hale. This parameter is called the
aid (2). asshovenin Figure? 10, For IH, the half-withof singlets oughtobe less

AE Some Urea NMR Sven

Bm Cm qi Dic SHO pom)
oben (eat TT
Ace Acida Nom mon m 6 ns
206) 200m)
Acetone 2056) 206703) u 20
390
Actor) 1946) 187 ns a
140
Benzene nm BAG) 5-0 23 os
Chlorofomn-¢ 170 MO a 48 15
Geloheranedis 130) 2646 6-8 20 Es
Do 430 Fat) as
Dichorometane- 5320) 00) 98 89 15
pDiocaned; 335m) 60 1-0 22 2a
DMFér aa) 1620 367 35
29215) 390
256 330
DMSO, 2506) Bm an aa
Methanol wo 820) nn 50
33169
Byrne, a3) 1904) 2-62 so
780 13590)
1201239)
THF Ay 3580) 6763) 0-6 16 as
a) 2540)
Tone Om 190 2a os
0m 1320)
698(@) 12830)
2005) 2550
204 (7)
Trad sou) a 5-7 AS us
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Dee

3. 2.10 Conan Iuris BR Sor

og Vic Ge saris
rc e rana Ls Gre

PURE 2 Some common inp in NMR.

[NMR impares. Water canbe oublesome andi often present in CDCI, as well as most
‘ther NMR solvents, but canbe minimized by storing the solvent in a desiccator. The
chemical shift ofthe water peak in various solvents is shown in Table 23. The wate level
an be reduced with ding agent, but molecular seves ae nt recommended because
they contain very fine dust, which can affect e resolution Oir commercial products
‘outnely used in te laboratory can creep nt sample and give ie to unexpected peaks.
io common examples are e phases from Tygon® tubing and grease used to ubica
round glas joins. Acetone i frequently used to wash ot NMR tubes and it ean persist
¥en when the tubes are placed in an oven (a simple rise with CDCI will sole this
problem). The spectra o these and otr relevant compounds appear in Figure 2.17. ist
‘Of shifts of common impares in various solvents is own in Table 24,

4. a redaction Naci Magnet Romane

ABLE 24 Sn ttf Comoe npc os Sor (pe (mo)

= Gin DMSO Piney Bammeds DO
Acte ASA 250 1556 200) 18 ET]
‘pense 276 220 2000 126) 226)
Assise 1986) 296) 180 0676) 2050)
Deere 79 100 730 100 746
Foot 1236) IMG DE os, 126)
colo 1210 256 EG 6416) =
Speichere, 100) mo 180 1400)
Diionedune 53000) mo $826) 466
po] 12 30 27)
En 15 L2@ 100
Dur so 1386)
2956) an 27@ 0
256) 200 2.6608) 19866)
uso 2626) 2326) 200 1916)
Doxa 3006) 3616 3 338)
Estan 32 109 3869 100
En mo 1@ 00
iy acre “a CT 3
2040) 206 10 1580)
1250 120 100 0m
Medio 186 ma II 3.096) 2.
po Eber 120) 12809 1200) 1220 =
0300) own TT) oo
ropa 405(m) am 37600)
1260 100 1 18
Propano 300 3350 3100 3610)
10m) 15m 10 1m 17
0930) oo os7@ 0, 059
Pride 30m Bm m ESO A
10m 7m 7m 7050) 730m)
728m Um m 50 1
me 374m) 364) 36) 35
185 us) mm IS) OS) 1386)
Tone 11960) 2m 72m m m
246 226 Re) 256
Tchyamise 25600) 270 200 0 290
1030 0990) 00 0950 LA
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