An insight into hexamethylenetetramine: a versatile reagent in organic synthesis

A simple new method for the determination of ammonium isotopes by gas chromatography-mass spectrometry

We report a new method for the determination of naturally abundant ¹⁵N (concentration of ¹⁵N) in ammonium (NH₄⁺) in water samples, including drinking water, surface water, groundwater, and seawater, by gas chromatography-mass spectrometry (GC-MS) based on the isotopic analysis of hexamethylenetetramine. The resulting product was obtained by the reaction between ammonium ions and formaldehyde under the given conditions (pH = 6.0, 40 °C, 30 min). Then, the species was extracted (with chloroform) and concentrated at pH = 8.5 and measured by GC-MS. The results showed that the relative standard deviation (RSD) of the δ¹⁵N measurements was less than 10% and the recoveries were in the range of 71-118% (n = 5). The limit of detection was 20 μmol l^-1. Compared to the previous method, the present method is simple and highly suitable to be used as a routine method for the ¹⁵N/¹⁴N analysis of NH₄⁺.

Synthesis of β-Silyl α-Amino Acids via Visible-Light-Mediated Hydrosilylation

An expedient synthesis of β-silyl α-amino acids is reported via the application of visible-light-mediated hydrosilylation. The reaction utilizes readily accessible and structurally diverse hydrosilanes to provide radicals for conjugate addition to dehydroalanine ester and analogues. Notably, the use of chiral methyleneoxazolidinone as the substrate and chiral inducer enabled the highly stereoselective synthesis. Furthermore, the reaction could also be performed in a continuous flow fashion and scaled up to the gram scale.

Production of glycerol by Lactobacillus plantarum NRRL B-4496 and formation of hexamine during fermentation of pea protein enriched flour

Suspensions of pea protein enriched flour (PP) inoculated with Lactobacillus plantarum NRRL B-4496 and uninoculated PP suspensions were incubated in vials covered with airtight caps. Organic compound compositions of fermented and unfermented PP suspensions (F-PP and U-PP, respectively) were analyzed using solid phase microextraction (SPME) coupled with gas chromatography - mass-spectrometry (GCMS). Acetic acid was detected in all samples; pH dropped from pH 6.5 to pH 4.1 in L. plantarum F-PP and to pH 5.3 in uninoculated F-PP. Abundance of acetic acid and minuscule presence of lactic acid in L. plantarum F-PP suggested that fermentation proceeded preferentially via the pyruvate formate lyase (PFL) pathway. Nonetheless, glycerol appeared to be the most abundant compound in L. plantarum F-PP samples; colorimetric analysis indicated that its average concentration in these samples was 1.05 g/L. A metabolic switch from the PFL pathway to glycerol production might occur due to acidity tolerance limitations of L. plantarum, glycerol production being associated with the release of phosphate, which can act as a buffer. Fermentation of PP by L. plantarum also led to formation of hexamine, which is a known food preservation agent. Presence of naturally formed hexamine and glycerol in food products may render using chemical additives needless.

Interfacial properties and impact toughness of dendritic hexamethylenetetramine functionalized carbon fiber with varying chain lengths

In order to understand the effects of chain length on the interfacial adhesion of PAN-based carbon fiber (CF)/epoxy composites, dendritic hexamethylenetetramine (HMTA) was functionalized on carbon fibers through quaternary ammonium salt reaction using alkyl dihalide of varying chain length [Cl(CH₂)_nCl, n = 2, 6 and 12].