2.3- Dibromopropionic acid

Numerous examples of unwanted or deliberate Pd-mediated homocoupling of organometallic reagents have been reported (Scheme 8.14) [38, 122, 123]. Suitable oxidants include a-halo ketones [116, 124, 125] (which can, therefore, not be used as electrophilic component in cross-coupling reactions), oxygen [120, 124, 126], 1,2-diiodoethene [127], 2,3-dibromopropionic acid esters [119], and CuCl2 [128]. 

Figure 6-12 The COSY90 (top) and COSY45 (bottom) spectra of 2,3-dibromopropionic acid.

The Selective Population Transfer (SPT) experiment is usually used in spin system analysis with a FT spectrometer. Normally the experimental SPT spectra are compared with calculated SPT spectra simulated using different combinations of coupling constant signs. In common with many textbooks the AMX spin system 2,3-dibromopropionic acid will be used to introduce the concepts behind the SPT experiment. The IH spin system parameters for 2,3-dibromopropionic acid are shown below. The only difference between Spin System A and Spin System B is the sign of the coupling constant J(H(2), H(3)), the results of SPT experiments will be used to distinguish between the two possible spin systems. 

In Check it 5.4.1.6 the E.COSY sequence using variable pulse phase for coherence selection is written and tested by simulating the E.COSY spectrum of 2,3-dibromopropionic acid. 

An alternative approach to tailor the cross peaks is the z-filtered COSY spectrum (z-COSY) [5.130]. In Check it 5.4.1.7 the "small-flip angle COSY" spectrum of 2,3-dibromopropionic acid, the basic sequence of the z-COSY spectrum, is simulated. As such a z-COSY spectrum can not be calculated because the randomly changing delay which is the major part of the z-filter can not be simulated in the current version of NMR-SIM. A comparison of the results of Check it 5.4.1.7 and the E.COSY spectrum of the same spin system calculated in Check it 5.4.1.6 shows that due to the small flip angles the diagonal peaks of the z-COSY spectrum are reduced in intensity while the cross peaks are very similar. 

CH2 CH.C(02)C3H7 mw 114.16 colorl liq bp 122.9° d 0.91996g/cc at 0°. Prepn is by redn with Zn in sulfuric acid of the propyl ester of oijjS-dibromopropionic acid dissolved in n-propanol... 

PROTON OF dibromopropionic acid in CDC13 TEMP=25C, Liquids 600 MHz NMR Instrument... 

Fig. 10.26. ID proton spectrum of dibromopropionic acid in deuterated chloroform.

Diaminopropionic Acid has not yet been described as a constituent of the proteins, but it was synthesised by Klebs in 1894 by the action of ammonia upon dibromopropionic acid. 

Propyl Acrylate (PropyUc Acid, Propyl ester). The (theoretical) parent compd for nitroolefm polymers used as proplnts and expls such as 2,2-Dinitropropylacrylate (DNPA) . See under this title in this Vol, N139-R to N140-L. CH2 CH.C(02)C3H7 mw 114.16 colorl liq bp 122.9° d 0.91996g/cc at 0°. Prepn is by redn with Zn in sulfuric acid of the propyl ester of O(,j3-dibromopropionic acid dissolved in n-propanol... 

CaHaBrMg Allylmagnesium bromide. 5 C3H6Br20, a, -Dibromopropionic acid 113 CaHsClaOa, o, -Dichloropropionic acid 113... 

In Check it 5.3.1.4 the x- and y-profiles of the transverse magnetization for a 270° Gaussian pulse [5.91], a 90° half-GAUSSiAN pulse [5.92] and a 90° Gaussian Pulse Cascade G4 [5.93] are compared. Finally the H spectra of dibromopropionic acid with selective excitation of the proton at 2.85 ppm is simulated for all three shaped pulses. 

The acid formed reacts with a part of the alkali present and is obtained as the potassium salt. It has been found in this and other cases that a halogen atom in the )3-position to the carboxyl group is readily removed in this way. a,/ -Dibromopropionic acid is converted into acrylic acid when treated with zinc in the presence of dilute sulphuric acid — ... 

The temperature at which the reaction is carried out, and the proportion of bromine used, determine the number of bromine atoms introduced. Thus, propionic acid when treated at 100° with phosphorus and bromine gives a-bromopropionic acid, CHsCHBr.COOH and at 220° with an excess of bromine, a, o-dibromopropionic acid, CH3CBr2.COOH. 

The formation of the acid from a, j3-dibromopropionic acid furnishes evidence of its structure —... 

Write equations for reactions by which (a) /3-hydroxycaproic acid may be converted into amylene, (h) propronic aldehyde into a-hydroxybutyric acid, (c) lactic acid into aa-dibromopropionic acid. 

Dibromo- 2-phenylpropionic acid, cinnamic acid dibromide, i-phenyl- 2-dibromopropionic acid)... 

---