.Continuous preparation of arylmagnesium reagents in flow with in-line IR monitoring

.Continuous preparation of arylmagnesium reagents in flow with in-line IR monitoring

T. Brodmann, P. Koos, A. Metzger, P. Knochel, S.V. Ley, Org. Proc. Res. Dev. 2012, 16, 1102-1113.

http://pubs.acs.org/doi/abs/10.1021/op200275d

A newly developed microscale ReactIR flow cell was used as a convenient and versatile inline analytical tool for Grignard formation in continuous flow chemical processing. The LiCl-mediated halogen/Mg exchange reaction was used for the preparation of functionalized arylmagnesium compounds from aryl iodides or bromides. Furthermore, inline IR monitoring was used for the analysis of conversion and possible byproduct formation, as well as a potential tool for elucidation of mechanistic details. The results described herein indicate that the continuous flow systems are effective for highly exothermic reactions such as the Grignard exchange reaction due to fast mixing and efficient heat transfer.

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Ethyl acetoacetate 乙酰乙酸乙酯 teaches you Organic spectroscopy… brush up?????

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Ethyl acetoacetate
Ethyl 3-oxobutanoate
Acetoacetic acid ethyl ester
Ethyl acetylacetate
3-Oxobutanoic acid ethyl ester


Ethyl acetoacetate is produced industrially by treatment of diketene with ethanol.
The preparation of ethyl acetoacetate is a classic laboratory procedure.[2] It is prepared via the Claisen condensation of ethyl acetate. Two moles of ethyl acetate condense to form one mole each of ethyl acetoacetate and ethanol.

Preparation of ethyl acetoacetate.







Structure: structure

IUPAC Name: ethyl 3-oxobutanoate (ethyl acetoacetate)

Analysis: C6H10O3: MW = 130.14

The molecule contains an oxygen, and from the analysis, contains two double bonds, carbonyls or rings.
The mass spectrum displays a molecular ion and the base peak represents the formation of the acylium ion, indicating the presence of a methyl adjacent to a carbonyl. The presence of an m-45 peak strongly suggests the presence of an ethoxy group.
The 13C spectrum contains six peaks, indicating that all carbons are unique. The quartets at  14 and 24 represent relatively simple methyl groups; the triplets at  59 and 47 represent a CH2 groups bonded to mildly electronegative groups; the singlets at  207 and 172 are in the carbonyl region, and most likely a ketone or aldehyde ( 207) and an ester ( 172).
The proton NMR shows evidence for an ethyl group and isolated CH2 and CH3 groups. The methylene of the ethyl group must be next to an electronegative atom (most likely oxygen) suggesting an -OCH2CH3 group. The isolated CH2 must also be flanked by mildly electronegative groups, and the isolated CH3 is in the region often observed for methyls adjacent to carbonyls.
The IR is consistent with a simple saturated hydrocarbon, possibly containing two carbonyls (based on the side peak at  1670 cm1). The minor peak at 3400 cm1 is too small to be an -OH.
The simplest structure which is consistent with all of these data would be a dicarbonyl compound containing an ethoxy residue and a methyl ketone (based on the presence of the acylium ion in the MS).

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1H NMR
NMR Spectrum
The proton NMR has a quartet coupled to a triplet, indicative of an ethyl group. The CH2 must be adjacent to an electron withdrawing group since it is shifted to  4.1. The two singlets at  2.2 and 3.2 suggest isolated CH2 and CH3 groups and the CH2 must be adjacent to one or more electronegative groups.

 

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13C NMR
13C NMR Assignments: C-13 assignments
13C NMR Data: q-13.6; q-24.2; t-59.2; t-46.6; s-172.0; s-207.1
The 13C spectrum contains six peaks, indicating that all carbons are unique. The quartets at  14 and 24 represent relatively simple methyl groups; the triplets at  59 and 47 represent a CH2 groups bonded to mildly electronegative groups; the singlets at  207 and 172 are in the carbonyl region, and most likely a ketone or aldehyde ( 207) and an ester ( 172).

spectrum for Ethyl acetoacetate

ethyl acetoacetate CH3COCH2COOCH2CH3

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MASS SPECTROSCOPY
Mass Spectrum


Mass Spectrum Fragments: C-13 assignments
The mass spectrum consists of a molecular ion at 130, an m-15 peak at 115, which is consistent with loss of a CH3 group, an m-43 peak (loss of acylium), an m-45 peak (loss of CH3CH2O-), and a base peak at m-43(m/e = 43) which suggests the formation of an acylium ion (CH3-CO). The spectrum is consistent with a molecule which can lose methyl or ethoxy radicals, or can undergo fragmentation to form the acylium radical cation.

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IR

3400-3200 cm1: no OH peak (too small) 3100 cm1: no significant peak, suggesting no unsaturated CH 2900 cm1: strong peak suggesting saturated CH 2200 cm1: no unsymmetrical triple bonds 1710 cm1: strong carbonyl with a second peak at 1670 cm1, suggesting a the possibility of two carbonyls 1600 cm1: no significant peaks, suggesting no carbon-carbon double bonds

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2D [1H,1H]-TOCSY

spectrum for Ethyl acetoacetate

spectrum for Ethyl acetoacetate1D DEPT135





spectrum for Ethyl acetoacetate2D [1H,13C]-HSQC



spectrum for Ethyl acetoacetate2D [1H,13C]-HMBC





spectrum for Ethyl acetoacetate2D [1H,1H]-COSY


spectrum for Ethyl acetoacetate2D [1H,13C]-HMQC

 

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Synthon identification in co-crystals and polymorphs with IR spectroscopy. Primary amides as a case study

Synthon identification in co-crystals and polymorphs with IR spectroscopy. Primary amides as a case study

CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE40286J, Paper
Arijit Mukherjee, Srinu Tothadi, Shaunak Chakraborty, Somnath Ganguly, Gautam R. Desiraju
IR marker bands are used to identify multiple synthons in polymorphs and co-crystals

IR spectroscopy has been widely employed to distinguish between different crystal forms such as polymorphs, clathrates, hydrates and co-crystals. IR has been used to monitor co-crystal formation and single synthon detection. In this work, we have developed a strategy to identify multiple supramolecular synthons in polymorphs and co-crystals with this technique.

The identification of multiple synthons in co-crystals with IR is difficult for several reasons. In this paper, a four step method involving well assigned IR spectral markers that correspond to bonds in a synthon is used. IR spectra of three forms of the co-crystal system, 4-hydroxybenzoic acid:4,4′-bipyridine (2 : 1), show clear differences that may be attributed to differences in the synthon combinations existing in the forms (synthon polymorphism).

These differences were picked out from the three IR spectra and the bands analysed and assigned to synthons. Our method first identifies IR marker bands corresponding to (covalent) bonds in known/model crystals and then the markers are mapped in known co-crystals having single synthons. Thereafter, the IR markers are queried in known co-crystals with multiple synthons.

Finally they are queried in unknown co-crystals with multiple synthons. In the last part of the study, the N–H stretching absorptions of primary amides that crystallize with the amide dimers linked in a ladder like chain show two specific absorptions which are used as marker absorptions and all variations of this band structure have been used to provide details on the environment around the dimer. The extended dimer can accordingly be easily distinguished from the isolated dimer.

CrystEngComm, 2013, Advance Article

Arijit mukherjee et al
DOI: 10.1039/C3CE40286J
Received 14 Feb 2013, Accepted 28 Mar 2013
First published online 02 Apr 2013

link

http://pubs.rsc.org/en/Content/ArticleLanding/2013/CE/C3CE40286J?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FCE+%28RSC+-+CrystEngComm+latest+articles%29