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NMR Chemical Shifts of Trace Impurities: Common …

2176 Organometallics 2010, 29, 2176 2179. DOI: NMR Chemical Shifts of Trace impurities : Common Laboratory solvents , Organics, and Gases in Deuterated solvents Relevant to the Organometallic Chemist Gregory R. Fulmer,*, Alexander J. M. Miller, Nathaniel H. Sherden, . Hugo E. Gottlieb, Abraham Nudelman, Brian M. Stoltz, John E. Bercaw, and Karen I. Goldberg .. Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, . Arnold and Mabel Beckman Laboratories of Chemical Synthesis and Caltech Center for Catalysis and Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, and Department of Chemistry, Bar Ilan University, Ramat Gan 52900, Israel Received February 11, 2010.

NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities Hugo E. Gottlieb,* Vadim Kotlyar, and Abraham Nudelman* Department of Chemistry, Bar …

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Transcription of NMR Chemical Shifts of Trace Impurities: Common …

1 2176 Organometallics 2010, 29, 2176 2179. DOI: NMR Chemical Shifts of Trace impurities : Common Laboratory solvents , Organics, and Gases in Deuterated solvents Relevant to the Organometallic Chemist Gregory R. Fulmer,*, Alexander J. M. Miller, Nathaniel H. Sherden, . Hugo E. Gottlieb, Abraham Nudelman, Brian M. Stoltz, John E. Bercaw, and Karen I. Goldberg .. Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, . Arnold and Mabel Beckman Laboratories of Chemical Synthesis and Caltech Center for Catalysis and Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, and Department of Chemistry, Bar Ilan University, Ramat Gan 52900, Israel Received February 11, 2010.

2 Tables of 1H and 13C NMR Chemical Shifts have been compiled for Common organic compounds often used as reagents or found as products or contaminants in deuterated organic solvents . Building upon the work of Gottlieb, Kotlyar, and Nudelman in the Journal of Organic Chemistry, signals for Common impurities are now reported in additional NMR solvents (tetrahydrofuran-d8, toluene-d8, dichloromethane-d2, chlorobenzene-d5, and 2,2,2-trifluoroethanol-d3) which are frequently used in organometallic laboratories. Chemical Shifts for other organics which are often used as reagents or internal standards or are found as products in organometallic chemistry are also reported for all the listed solvents .

3 Hanging above the desk of most every chemist whose work ethylene, propylene, and carbon dioxide) often encoun- relies heavily on using NMR spectroscopy1 is NMR Chemi- tered as reagents or products in organometallic reactions, cal Shifts of Common Laboratory solvents as Trace Impu- along with organic compounds relevant to organometallic rities by Gottlieb, Kotlyar, and By compiling chemists (allyl acetate, benzaldehyde, carbon disulfide, the Chemical Shifts of a large number of contaminants carbon tetrachloride, 18-crown-6, cyclohexanone, diallyl commonly encountered in synthetic chemistry, the publica- carbonate, dimethyl carbonate, dimethyl malonate, furan, tion has become an essential reference.

4 Allowing for easy Apiezon H grease, hexamethylbenzene, hexamethyldisil- identification of known impurities in a variety of deuter- oxane, imidazole, pyrrole, and pyrrolidine), have also ated organic solvents . However, despite the utility of been added to this expanded list. Gottlieb et al.'s work,3 the Chemical Shifts of impurities in a number of NMR solvents often used by organometallic Experimental Section chemists were not included. Tetrahydrofuran-d8 (THF-d8), toluene-d8, dichloromethane-d2 (CD2Cl2), chlorobenzene-d5 All deuterated solvents were obtained commercially through (C6D5Cl), and 2,2,2-trifluoroethanol-d3 (TFE-d3) are com- Cambridge Isotope Laboratories, Inc.

5 NMR spectra were monplace in laboratories practicing inorganic syntheses. recorded at 298 K using 300, 500, or 600 MHz spectrometers Therefore, we have expanded the spectral data compilation (13C{1H} NMR frequencies of , 126, or 151 MHz, res- with the inclusion of Chemical Shifts of Common impurities pectively). Adopting the previously reported strategy,2 standard solutions of mixtures of specific impurities were used to reduce recorded in the deuterated solvents heavily employed the number of necessary individual NMR experiments. The in our organometallic laboratories. The Chemical Shifts combinations of organic compounds were chosen in a way in of various gases (hydrogen, methane, ethane, propane, which intermolecular interactions and resonance convolution would be minimized.)

6 Unless otherwise stated, the standard *To whom correspondence should be addressed. E-mail: fulmerg@ solutions were prepared with qualitatively equal molar amounts of the following compounds: (solution 1) acetone, dimethylform- (1) For general information on 1H and 13C{1H} NMR spectroscopy, amide, ethanol, toluene; (solution 2) benzene, dimethyl sulf- see: Balc! , M. Basic 1H- and 13C-NMR Spectroscopy; Elsevier: Amsterdam, oxide, ethyl acetate, methanol; (solution 3) acetic acid, chloro- 2005. form, diethyl ether, 2-propanol, tetrahydrofuran; (solution 4). (2) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem.

7 1997, acetonitrile, dichloromethane, 1,4-dioxane, n-hexane, hexa- 62, 7512. (3) According to ACS Publications as of December 2009 (http://pubs. methylphosphoramide (HMPA); (solution 5) 1,2-dichloroethane, ), Gottlieb et al.'s publication2 is the most downloaded Journal n-pentane, pyridine, hexamethylbenzene; (solution 6) tert-butyl of Organic Chemistry article over the preceding 12 months. alcohol, 2,6-di-tert-butyl-4-methylphenol (BHT), cyclohexane, Published on Web 04/16/2010 r 2010 American Chemical Society 7512 J . Org. Ch em . 1997, 62, 7512-7515. N MR Ch e m ic a l S h ifts o f Co m m o n La bo ra to ry S o lv e n ts a s Tra c e Im p u ritie s H u go E.

8 Got t lieb,* Va dim Kot lya r , a n d Abr a h a m Nu delm a n *. Departm en t of Ch em istry, B ar-Ilan Un iversity, R am at-Gan 52900, Israel R eceived J u n e 27, 1997. In t h e cou r se of t h e r ou t in e u se of NMR a s a n a id for or ga n ic ch em ist r y, a da y-t o-da y pr oblem is t h e iden tifica - t ion of sign a ls der ivin g fr om com m on con t a m in a n t s (wa t er , solven t s, st a bilizer s, oils) in less-t h a n -a n a lyt i- ca lly-pu r e sa m ples. Th is da t a m a y be a va ila ble in t h e lit er a t u r e, bu t t h e t im e in volved in sea r ch in g for it m a y be con sider a ble. An ot h er issu e is t h e con cen t r a t ion depen den ce of ch em ica l sh ift s (especia lly 1 H ); r esu lt s obt a in ed t wo or t h r ee deca des a go u su a lly r efer t o m u ch F ig u re 1.

9 Ch em ica l sh ift of H DO a s a fu n ct ion of t em per a - m or e con cen t r a t ed sa m ples, a n d r u n a t lower m a gn et ic t u r e. fields, t h a n t oda y's pr a ct ice. We t h er efor e decided t o collect 1 H a n d 13 C ch em ica l depen den t (vid e in fra). Also, a n y pot en t ia l h ydr ogen - sh ift s of wh a t a r e, in ou r exper ien ce, t h e m ost popu la r bon d a ccept or will t en d t o sh ift t h e wa t er sign a l down - ext r a pea ks in a va r iet y of com m on ly u sed NMR field; t h is is pa r t icu la r ly t r u e for n on pola r solven t s. In solven t s, in t h e h ope t h a t t h is will be of a ssist a n ce t o con t r a st , in DMSO t h e wa t er is a lr ea dy st r on gly t h e pr a ct icin g ch em ist.

10 H ydr ogen -bon ded t o t h e solven t , a n d solu t es h a ve on ly a n egligible effect on it s ch em ica l sh ift . Th is is a lso t r u e Ex p e rim e n ta l S e c tio n for D 2 O; t h e ch em ica l sh ift of t h e r esidu a l H DO is ver y NMR spect r a wer e t a ken in a Br u ker DP X-300 in st r u m en t t em per a t u r e-depen den t (vid e in fra) bu t , m a ybe cou n t er - ( a n d MH z for 1 H a n d 13 C, r espect ively). Un less in t u it ively, r em a r ka bly solu t e (a n d pH ) in depen den t . ot h er wise in dica t ed, a ll wer e r u n a t r oom t em per a t u r e (24 ( 1 We t h en a dded 3 L of on e of ou r st ock solu t ion s t o C).)


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