Amount Of Primary Amine Research Articles

Functional Groups Accessibility and the Origin of Photoluminescence in N/O‐containing Bottom‐up Carbon Nanodots

AbstractChemical surface functionalization of carbon nanodots (CNDs) offers a valuable opportunity to tailor multifunctionality in these nanocarbons, by engineering the composition of their molecular surface. Therefore, it is important to elucidate the type and amount of CNDs surface functionalization to be able to design their properties accurately. CNDs are often functionalized through amide coupling without validating the degree of surface functionalization. As a measure of surface functionalization, the amounts of primary amines via Kaiser test (KT) or imine reactions of the bare CNDs is often considered. However, this may lead to overestimating the degree of surface functionalization obtained by the pure amide coupling due to different reaction mechanisms and involved intermediates. Herein, four different CNDs prepared by microwave‐assisted synthesis from arginine or citric acid with varying amounts of ethylenediamine are presented. We resorted to combining physicochemical methods to provide elemental, structural, and optical information. By that, we developed a method to quantify the degree of surface functionalization by amide coupling and show that the surface functionalization is lower than anticipated. Comparing experimental optical features of the CNDs with different computed model systems enables us to provide a more advanced vision of structure‐property relationships in these still elusive nanocarbons.

Grafting of N‐moieties onto octa‐methyl polyhedral oligomeric silsesquioxane microstructures by sequential continuous wave and pulsed plasma

A functionalization of microstructures of polyhedral oligomeric silsesquioxane (POSS) to obtain substrates contain N‐moieties, with a probable high selectivity of primary mines is demonstrated for the first time in a low pressure plasma process through a sequential continuous wave plus pulsed mode (CW + P). Selective grafting of N‐moieties was performed across octa‐methyl POSS micro‐powder by substituting hydrogen atoms of the terminal methyl groups during nitrogen/hydrogen (N2/H2) gases plasma. As opposed to wet chemical functionalization approaches, the plasma method does not require reactive chemicals and is environmentally friendly. The results demonstrate the efficiency of the treatment (N/Si) reaches 7.1% with an indication of high NH2 selectivity (NH2/N). The amount of primary amines is determined from XPS data after 4‐(trifluoromethyl) benzaldehyde (TFBA) chemical derivatization.

Storage-induced changes in the sensory characteristics and volatiles of conventional and lactose-hydrolyzed UHT processed milk

Storage-induced changes are known to be more prominent in lactose-hydrolyzed (LH) milk compared to conventional milk. Therefore the present study aimed at identifying off-flavors resembling from formation of volatiles during storage of ultra-high temperature treated (UHT) LH milk and conventional UHT milk. Further, the influence of heat processing, indirect or direct, on UHT LH milk was also examined. Storage-induced changes in sensory attributes, volatiles and primary amines were investigated during a 4 months period. Conventional UHT milk (with 5 % lactose) processed using indirect heat treatment (CONVI) and two types of UHT LH milk (with less than 0.01 % lactose) produced using either direct heat treatment (LHD) or indirect heat treatment (LHI) were represented in the study. Sensory descriptive analysis showed that fresh samples of CONVI, LHI and LHD differed in sensory properties and the samples could be differentiated according to boiled and stale aroma as well as color saturation. Differentiation of the fresh samples based on the volatile gas chromatography–mass spectrometry profile was not achievable. During storage, samples developed differently with respect to sensory characteristics, volatiles and the amount of primary amines. Partial least squares models (PLS1) including only methyl ketones and aldehydes showed that 2-butanone, 2-pentanone, 2-heptanone, 2-nonanone, heptanal, octanal and nonanal predicted stale flavor. Bitter taste, on the other hand, correlated with the amount of primary amines (Pearson’s correlation, r 2 = 0.71). This finding indicates that storage-induced changes in sensory characteristics, volatiles and primary amines depend on both differences in lactose content and the applied heat processing.

Preparation and characterization of thermoresponsive hyperbranched polyethylenimine with plenty of reactive primary amine groups

Certain amount of primary amine (NH2) groups of hyperbranched polyethylenimine (HPEI) was first protected by Boc groups. Subsequently, the residual reactive amine groups were reacted with isobutyric anhydride to introduce isobutyramide (IBAm) groups to HPEI. Finally, Boc groups were deprotected to result in HPEI-IBAm-NH2 with 18% of primary amine terminals on the periphery and 80% of IBAm terminal groups (abbreviated as HPEI-IBAm0.80-NH2). 1H-NMR characterization proved the successful preparation of the product in each step. Compared with its spatial isomer HPEIIBAm0.80 without primary amine groups, 1H-NMR spectra verified that more IBAm groups were located in the interior of HPEI-IBAm0.80-NH2. The further modification of HPEI-IBAm0.80-NH2 and HPEI-IBAm0.80 with p-nitrobenzaldehyde demonstrated that HPEI-IBAm0.80-NH2 was more reactive than HPEI-IBAm0.80 due to its possession of primary amines. Turbidimetry measurements showed that HPEI-IBAm0.80-NH2 was thermoresponsive in water. In the pH range of 9.5–10 its cloud point temperature (T cp) was constant, and it increased obviously upon decreasing the pH below 9.5. The thermoresponsive HPEI-IBAm0.8 exhibited the similar trend, but the pH threshold to achieve the constant T cp was around 8.5. Moreover, HPEI-IBAm0.8-NH2 showed higher T cp and broader phase transition than HPEI-IBAm0.8. The mechanism leading to the different thermoresponsive properties between HPEI-IBAm0.8-NH2 and its spatial isomer HPEI-IBAm0.8 was discussed.

Proline-Rich Cytokine from Neurosecretory Granules: A New Natural Substrate for Dipeptidyl Peptidase IV

A proline-rich cytokine from neurosecretory granules of bovine neurohypophysis, 15 amino acids containing PRP-1 (Ala-Gly-Ala-Pro-Glu-Pro-Ala-Glu-Pro-Ala-Gln-Pro-Gly-Val-Tyr), had been demonstrated as a unique regulator of activity of neurons, strong antibacterial agent, and mediator of the hypothalamus-neurohypophysis-bone marrow-thymus axis, which participates in hematopoietic stem cells differentiation. In the present work it was shown that this neuropeptide represents a new natural substrate for Dipeptidyl Peptidase IV (DPPIV). The time-dependent increase of primary amines quantity in the assay mixture of PRP-1 and DPPIV has been observed allowing to conclude, that DPPIV catalyses the enzymatic reaction of PRP-1 cleavage. The amount of primary amines in the assay mixtures was evaluated using o-phtaldialdehyde dye. The gel-filtration and paper electrophoresis analyses proved this conclusion. The catalytic parameters of catalyzed by DPPIV enzymatic reaction of PRP-1 cleavage were determined as: V(max) = 1.27 ± 0.11 nmol/min and K(m) = 0.38 ± 0.1 mM.

Plasma Deposition of Allylamine on Polymer Powders in a Fluidized Bed Reactor

AbstractSummary: Thin films of plasma‐polymerized allylamine (PPAA) have been deposited onto polyethylene powders (PE) and polystyrene (PS) beads by using a low‐pressure 13.56 MHz plasma in a fluidized bed reactor. Chemical derivatization using a set of three different blocking agents has allowed quantitative measurement of the relative percentages of primary, secondary, and tertiary amines. Under optimized conditions, it is possible to incorporate up to 110 nmol of amine groups per gram of powder and with a selectivity of 75% for primary amines. Moreover, our data clearly show that for films deposited at 10 W the selectivity for primary amines is at a maximum, but this is at the expense of resistance to washing. A power of 20 W corresponds to an optimum value since both the amount of primary amines and the degree of resistance of the coating to solvents reach maximum values.Distribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.imageDistribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.

SELECTIVE N-ALKYLATION OF PRIMARY AMINES WITH CHLOROACETAMIDES UNDER pH-CONTROLLED AQUEOUS CONDITIONS

ABSTRACT A practical method for selective alkylation of primary amines with chloroacetamides under modified Finkelstein conditions using stoichiometric amounts of sodium iodide in acetonitrile/water is described. An interesting finding in this study was that α-alkylaminoacetamides are less basic than the corresponding primary alkylamines by about 2 pKa units; this necessitated a pH of 12 during alkylation to optimize the monoalkylation selectivity. Depending on the amount of primary amine used, mono : dialkylation selectivities ranged from 2.7 to 10.

Applications of simultaneous DSC/FTIR analysis

A combination of the standard laboratory techniques differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR) spectroscopy is described. This simultaneous DSC/FTIR technique gives spectroscopic and thermodynamic information about a solid or liquid sample undergoing thermal modification. DSC measures the exothermic and endothermic responses of the samples, while the FTIR analysis observes their changes in chemical and physical composition. Reflectance infrared microspectroscopy was employed to examine the samples. Two epoxy samples were studied by DSC/FTIR. Both samples were mixtures of diglycidyl ether of Bisphenol A with a cycloaliphatic primary amine. The two samples differed only in the amount of primary amine used to crosslink the epoxy resin. The cure of each specimen was studied by using the reflectance/absorbance mode of infrared analysis, while simultaneously undergoing a DSC experiment. Samples were monitored as a function of secondary amine content, crosslink density, and hydroxyl formation. This information was used to examine whether the samples differed in their overall reaction rates. The samples did in fact exhibit markedly different cure character, giving insight into the reaction routes and a prediction of the final molecular structures achieved by these small changes in the ratio of resin to amine activator. A sample of poly(ethylene terephthalate) (PET) was also analyzed by DSC/FTIR; in this case the specular reflectance mode of infrared analysis was employed. DSC was used to detect the glass transition, multiple melting endotherms and recrystallization of the polymer as it was heated and cooled. FTIR was used to monitor structural changes in the sample as it went through these thermal transitions. These experiments demonstrate the high potential of DSC/FTIR reflectance microspectroscopy when studying the thermal characteristics of materials.

The photochemical decomposition of alkyl azides

Abstract A study has been made of the products resulting from the solution photolyses of n-butyl azide, n-ocytl azide, 4-phenyl-1-butyl azide, α-azidobutyric acid, α-azidoisobutyric acid, azidodiphenylacetic acid, ethyl α-azidobutyrate, α-azidovaleric acid, and ethyl α-azidovalerate. The effect of variations in solvent and temperature has been investigated as well as the influence of benzophenone photosensitization and iodine catalysis. In the case of the first three azides the predominant product (besides nitroen) under all photolytic conditions studied was the aldimine formed by 1,2-hydrogen migration. Hydrogen abstraction probably from solvent accounted for small amounts of primary amine. 1,2 Alkyl migration accounted for the formation of some of the lower homologous amine. Also secondary amine (1–2%) formed by insertion into the solvent cyclohexane was observed. Photolysis of the α-azido acids in methanol solution resulted in efficient decarboxylation and aldimine formation. Minor amounts of amino acid formed presumably via hydrogen abstraction from solvent were also obtained. In the case of azidodiphenylacetic acid, phenyl group migration occurs in competition with direct loss of esters. α-Deuterio-α-azidobutyric acid has been synthesized and photolysed for the purpose of determining the sequence of steps in the photodecarboxylation reaction. Intramolecular photocyclization of alkyl azides to form pyrrolidine derivatives has been found to be a highly irreproducible process. 1 2 In initial experiments in our laboratory we succeeded in obtaining 2-n-butylpyrrolidine by irradiation of octyl azide. Subsequently we were unable to reproduce this result although as far as possible essentially identical reaction conditions were employed. In a private communication from Prof. D. H. R. Barton we have learned that he so far had been unsuccessful in repeating the original photolytic cyclization of azides. In addition to the work reported in this paper, research continues in our laboratory directed towards resolving these ambiguities. In the systems studied this pathway accounted for only a very minor amount of product or none at all. The stability of pyrrolidine under the photolytic and work up conditions was established. In spite of the large number of experimental variations employed, the yield of cyclic product could not be improved. Conditions for high yield cyclization have not been defined in the present investigation; and based upon results obtained, the photochemical decomposition of alkyl azides does not appear to be a generally useful method for pyrrolidine synthesis. The mechanism of the photolyses is discussed in terms of the possible formation of an alkyl nitrene and subsequent intervention of other intermediates. For the α-azido acids, a dual mechanism for decarboxylation is discussed involving the α-nitreno acid and α-imino acid.