2- maleimide spectra

Both the infrared and ultraviolet spectra of pyrrolidine-2,3,5-triones (75) have been interpreted to support their existence as hydroxy-maleimides (76), and the occurrence of a strong OH stretching band in the infrared spectrum of 4-phenylpyrrolidine-2,3,5-trione has been taken as evidence that it too exists in a hydroxy form, probably 76 (R CeHg). However, the trioxo formulation is suggested by t/j the infrared spectra of jV-substituted pyrrolidine-2,3,5-triones, although an equilibrium apparently occurs depending upon the substituents and conditions. The zwitterion formulation 77 has been advanced for 4-aminopyrrolidine-2,3,5-trione. For chemical evidence... 

Although maleimides form ground-state complexes with benzene, such complexes are not responsible for the occurrence of the photoaddition. Their absorption spectra are hidden below the absorption spectrum of benzene and do not extend beyond 270 nm, yet excitation above 280 nm readily leads to photoaddition of maleimide and some of its /V-substi tutcd derivatives. The mechanism proposed by Bryce-Smith [38,46] accounts for all of the facts (Scheme 13). 

Figure 1. C-NMR spectrum of poly (styrene-co-N-(p-t-butyloxy carbonyloxyphenyl) maleimide ...

To verify that this library was successfully synthesized, a portion of the resin was removed, and the compounds were cleaved from the polymer with trifluoroacetic acid and analyzed with HPLC electrospray ionization mass spectrometry. All the compounds shown could be identified. On cyclo-addition of the maleimides, endo/exo isomers and -in the case of the vinylsulfones - regioisomers were obtained. This led to complex chromatograms of isomeric compound mixtures co-elution often occurred. Quantification of the single compounds was not possible, and the peak area in the UV trace (detection at 214 nm) did not correlate with those of the total ion current chromatogram in the mass spectrum. 

Dihydroarcyriarubin-B (500) is a colourless compound which gives a red spot on silica gel plates which gradually turns to dark green on exposure to air. In the infrared spectrum (KBr) of (500) two absorptions, at 1770 and 1710 cm were indicative of the dihydromaleimide moiety, and in the H-n.m.r. spectrum the components of an AB-quartet centred, respectively, at 5 4.48 and 4.53 (/=6Hz) could be assigned to the protons of the maleimide ring. The structure of dihy-droarcyriarubin-B has been confirmed by hydrogenation of a second... 

A green pigment, arcyriaverdin-C, exhibited spectra in accord with the symmetrical structure (504) 156). Due to the deshielding effect of the maleimide carbonyl groups the signals of the protons at C-4 and C-4 in (504) resonate at 5 8.65 in the H-n.m.r. spectrum, a down-field shift when compared to the corresponding protons in (503). Ar-cyriaverdin-C has been chemically correlated with arcyriarubin-C (503) by oxidation of the latter with lead tetra-acetate in chloroform (/5d, 593). 

Arcyriacyanin-A, a green-blue pigment from Arcyria nutans was found to be isomeric with arcyriaflavin-A and exhibited mass and infrared spectra in accord with the presence of a maleimide moiety. In the H-n.m.r. spectrum the lack of signals from protons at the positions 2- and 4 - in the indole rings was taken to indicate bond formation... 

Maleimide and derivatives such as N-phenylmaleimide can be polymerized with triphenylphosphine as initiator [41] to give products with the repeat unit (7). The NMR spectrum of the polymer dissolved in d -dimethylsulphoxide contained signals at —28.3 and —13.4ppm (referenced to H3PO4) attributed to phosphonium salts and ylids, respectively, thought to be present as end-groups (8) and (9). 

Figure 4.7 Normalized absorbance spectra of double-labelled Im9 S81C before (dashed line) and after (dotted line) removal of excess un-conjugatedAlexa Fluor 488 C5 maleimide.The normalized absorbance spectrum expected for a 1 1 mixture of Alexa Fluor 488 C5 maleimide and Alexa Fluor 594 C5 maleimide is shown (continuous line) for comparison.

Purification and Characterization. RecrystaUize the crude N-phenyl-maleimide from cyclohexane using the Craig tube, to yield canary-yeUow needles. After drying the product on filter paper, or on a porous clay plate, weigh the crystals and calculate the percent yield. Determine the melting point and compare your result with the value given by Cava et al. (Bibliography section). Obtain an IR spectrum and compare it with that of an authentic sample or with that shown in the literature The Aldrich Library of IR Spectra and/or SciFinder Scholar). 

To modify the surfaces entirely (and not spatially resolved as shown with PCBAAm in the previous example) with streptavidin, the tetrazole-functionalized cellulose filter papers were immersed in a solution of maleimide-functionalized streptavidin in phosphate-buffered saline and irradiated. The success of the streptavidin immobilization was ascertained by XPS analysis. A significant increase in the C-C/C-H compared to the tetrazole-functionalized surfaces is in agreement with the presence of the protein on the cellulose fibers. Additionally, a significant increase from 6.0 at % to approximately 11.6 at% is observed in the Nls spectrum. The visual proof can be depicted by the remarkably bright fluorescence (excitation wavelength = 366 nm), whereas the control sample shows, as expected, no fluorescence. It is envisioned that the strategy can be translated to the development of novel bioactive papers and microfluidic paper-based analytical devices necessary for forthcoming developments in medicine. 

Maleimide. Maleimide and maleic anhydride are simple olefins and very useful molecules in organic syntheses for introducing various substituents. Addition reactions, cyclodimerization, Diels-Alder reactions and polymerization reactions are as well-known as their photochemical reactions. They are also known as electron acceptors in photoinduced electron-transfer reactions. The photosensitized reaction of maleimide with xanthone in 2-propanol has been investigated by TR EPR. The emissive CIDEP spectrum observed in 2-propanol is predominantly assigned to two kinds of maleimide alkyl-type radicals. On the other hand, the absorptive spectrum of the maleimide radical-anion was observed in 2-propanol in the presence of hydrochloric acid. The hydrochloric acid addition effect on the CIDEP patterns indicates the existence of two mechanisms for the photosensitization of maleimide by xanthone. One is a T-T energy transfer to maleimide followed by hydrogen abstraction by maleimide... 

Figure 12 Vibrational spectra of Af-phenylmaleimide (A) infrared, (B) Raman, (C) INS (D) INS spectrum of Af-(perdeutero-phenyl)maleimide (INS data recorded with TFXA at ISIS).

Analysis of the reaction mixture (after quenching and dialysis) via SEC yielded two broad fractions of different sizes, which were identified as 1 and unreacted maleimide-functionalized LMWH via H NMR (data not shown). SEC also showed the absence of a peak at the expected elution volume for the thiol-terminated four-arm star PEG, indicating that the star PEG was completely consumed during the reaction. Characterization of the fraction with the largest hydrodynamic volume via H NMR spectroscopy showed the expected resonance from the ethylene oxide protons of the star PEG backbone at 3.70 ppm, along with resonances from LMWH at 3.38-5.43 ppm in D2O. Integration of the relevant peaks (PEG backbone vs. LMWH) in the NMR spectrum... 

---