Validation gaps in Chemistry

Representative open questions

Showing 30 of 148 — one per source paper, highest-quality first.

• Real-time P$$_2$$O$$_5$$ quantification in industrial phosphoric acid using laser-induced breakdown spectroscopy: a paradigm shift in process analytical chemistry (2026) · doi

  The current LIBS calibration for P2O5 quantification was established using volumetrically diluted industrial stock solutions with representative impurities (Fe, Al, Mg, silicates), but the model has not been validated against dynamic matrix effects encountered in active wet-process phosphoric acid production streams, including acid viscosity fluctuations and suspended solids such as calcium sulfate (gypsum).

• Mechanistic investigations of the formation of multifunctional products from the multi-generation ●OH oxidation of styrene (2026) · doi

  The structures of some specific multi-generation oxidation products of styrene remain uncharacterized in laboratory chamber experiments and are merely inferred from exact mass and fragmentation data rather than definitively identified through experimental spectroscopic techniques.

• Donor-length engineering in directly linked covalent heptazine frameworks for photocatalytic H2O2 Production (2026) · doi

  The EPR spin-trapping experiments for ·OH detection using DMPO were conducted in purely aqueous solution under Ar-bubbling conditions; the detection and quantification of ·OH radicals in the presence of competing solutes (e.g., humic acids, inorganic ions) and at varying dissolved oxygen concentrations for H2O2 photosynthesis on heptazine catalysts have not been systematically studied.

• High-Entropy Catalysts for Biomass-Derived Chemicals Valorization: Mechanisms, Applications, and Opportunities (2026) · doi

  While particle size engineering has been identified as critical for tuning active site exposure, lattice distortion degree, and mass transfer efficiency in high-entropy catalysts, the specific size ranges (nanometer scale thresholds) that optimize configurational diversity and entropy effects for individual biomass valorization reactions (HMF, furfural, glucose, glycerol transformations) have not been systematically characterized.

• Green Dispersive Liquid–Liquid Microextraction Using an Octanol-Menthol-Based Deep Eutectic Solvent for Sensitive UV–Vis Determination of Rhodamine B in Food and Water Samples (2026) · doi

  The UV–Vis spectrophotometry detection in the DLLME-OCT-MEN-DES method exhibits limited selectivity in complex matrices with overlapping absorbance characteristics; complex samples with high matrix interference, such as food items with vibrant colours or high organic loads, were not included in this validation study.

• Photochemistry and photophysics of transition metal complexes: Quantum chemistry (2015) · doi

  Discrete QM/MM models describing H2O/dppz interactions have been applied to [Ru(phen)2(dppz)]2+ and [Ru(tap)2(dppz)]2+ in aqueous solution, but systematic comparison of PCM continuum versus discrete water models across all three ancillary ligand variants (phen, tap, bpy) with experimental luminescence data at multiple wavelengths (590-680 nm range) is needed.

• The role of the bis-trimethylsilylamido ligand, [N{SiMe3}2]−, in main group chemistry. Part 1: Structural chemistry of the s-block elements (2015) · doi

  The bioinorganic-inspired [Fe4S4] cubane cluster chemistry with amide-ligated systems includes examples with –N{SiMe3}2 ligands, but the specific structural roles and electronic effects of the bis-trimethylsilylamido ligand in modulating the redox properties of these cubanoid clusters have not been directly compared across different charge states (4+, 3+, 2+).

• Widespread use of sanitising products introduces chemicals of concern into human and environmental systems (2026) · doi

  The predictive accuracy of QSAR models for sanitizing product chemical toxicity requires validation improvements, as noted in reference 40. Current QSAR models need benchmarking specifically against the chemical constituents in antimicrobial sanitizers and hand hygiene products to establish reliable toxicity predictions for novel preservatives.

• Christmas chemistry A–Z (2014) · doi

  The paper claims resveratrol in red wine provides health benefits for heart disease, cancer, Huntington's, and Alzheimer's through superoxide elimination via manganese-containing enzymes, but does not specify which manganese enzyme catalyzes this reaction or provide quantitative data on resveratrol bioavailability and effective dosage required for these claimed therapeutic effects in humans.

• Olympian colour chemistry (2012) · doi

  The paper identifies that additives intended to stabilise photochromic dyes can produce undesired consequences such as altering photocolouration kinetics or generating residual colour in the non-activated state, but does not quantify the threshold concentrations or structural modifications of spirooxazines and naphthopyrans at which these side effects become problematic versus acceptable for commercial lens applications.

• Biosensors: Enzyme Immobilization Chemistry (2018) · doi

  The paper acknowledges that entrapment-based enzyme immobilization using electropolymerized polyaniline and polyacrylamide creates significant diffusional barriers for large molecular mass substrates and products, but does not specify which substrate/product molecular weights have been tested or at what size threshold diffusion becomes prohibitive for biosensor performance.

• Methyl 2-deoxy-3,5-di-O-p-toluoyl-α-d-ribofuranoside: isolation, crystal structure and conformation (2026) · doi

  The paper presents X-ray crystallographic data for the isolated compound but does not report solution-phase NMR conformational studies or molecular dynamics simulations to validate whether the solid-state conformation observed in the crystal structure is maintained in solution, which is critical for understanding its reactivity as a glycosylation donor.

• Transmetallation Reaction of Alkali and Alkaline-earth Metal Ions in Supramolecular Complex of [{Au6Cd3(tdme)2(D-pen)6}Cd4Na4](NO3)12 (2026) · doi

  The transmetallation reactions were investigated exclusively under solid-state single-crystal-to-single-crystal conditions. Whether the selectivity patterns and mechanistic insights (metal-linker exchange but not metal-center exchange) hold in solution-phase transmetallation or under different synthetic conditions (temperature, solvent, reaction time variations) remains unexamined.

• Synthesis of Tetravalent Boron Complexes with Pyrazolone-Based Ligand and their Drug-Likeness (2026) · doi

  The study evaluated drug-likeness of tetravalent boron complexes (MPAP-1 to MPAP-6) using computational physicochemical properties against five rule sets (Lipinski, Ghose, Veber, Egan, Muegge), but did not conduct in vitro absorption, distribution, metabolism, and excretion (ADME) studies or cell-based bioavailability assays to experimentally validate the predicted oral bioavailability of these pyrazolone-based boron coordination compounds.

• Physical Organic Chemistry (POC) Makes Chemistry a Science: A Personal Reflection on POC (2016) · doi

  The paper demonstrates AI-discovered chemical rules with statistical significance (p < 0.01, probability 0.90) but does not address validation mechanisms for translating these computational correlations into mechanistic insights. Methods are needed to experimentally verify whether AI-identified patterns (e.g., C-O bond effects on detonation velocity) have genuine chemical causality versus spurious correlation.

• Basic Organometallic Chemistry (2016) · doi

  The paper demonstrates that Zeise's salt undergoes hydrolysis and nucleophilic displacement reactions, but does not systematically compare reactivity patterns or substitution rates with other metal-alkene complexes containing different transition metals or different alkene ligands.

• Initial organotin chemistry (2014) · doi

  The equilibrium reaction between (C2H5)3SnOH and the dinuclear (C2H5)3SnOSn(C2H5)3 in response to atmospheric humidity has been proposed but not rigorously quantified; equilibrium constants and the effect of temperature and humidity gradients on this condensation reaction need experimental determination.

• Using quantum chemistry to estimate chemical shifts in biomolecules (2020) · doi

  The fragment-based QM/MM approaches for NMR chemical shift calculations (AFNMR, fragment density functional theory) have not been systematically compared across different fragmentation schemes and boundary treatments for large protein complexes exceeding 300 amino acids.

• Bis (N-Heterocyclic Carbene) Palladium Complex Immobilized Onto Fe3o4@Sio2 as a Catalyst for Sonogashira (Amine/Copper Free) and Hiyama Coupling of Arbr/Cl in Green Media (2026) · doi

  Catalyst loading optimization (entries 14-17 in Table 1) shows that reducing catalyst from 20 mg drastically decreases yield, but the specific minimum active site concentration required for efficient Sonogashira coupling and the relationship between Fe3O4@SiO2 support particle size and catalytic turnover frequency are not reported. Characterization of active site density and heterogeneity across catalyst batches would validate reproducibility.

• Coordination chemistry of poly(thioether)borate ligands (2010) · doi

  The side-on [PhTtAd]Ni(O2) complex is described as potentially lying on the superoxo-to-peroxo continuum based on DFT-derived O–O distances, but experimental methods to definitively distinguish between nickel(II)-superoxo versus more activated peroxo character through spectroscopic techniques beyond EPR and computational modeling have not been demonstrated.

• Evaluation of Octaethyl-7,17-dioxobacteriochlorin as a Ligand for Transition Metals (2020) · doi

  The successive-standard-addition UV-vis titration method employed for kinetic monitoring was limited to wavelengths with r² > 0.998 linearity. Extension of this quantitative approach to other spectroscopic techniques (HPLC, mass spectrometry, NMR) for concurrent tracking of metal insertion into octaethyl-7,17-dioxobacteriochlorin has not been explored.

• Coordination chemistry of tris(azolyl)phosphines (2018) · doi

  The tris(sulfide) variant SP(1,2,4Tz)3 reportedly affords higher yields in phosphorylation reactions compared to the oxide OP(1,2,4Tz)3, but comprehensive comparative studies across multiple substrate classes (nucleosides, amino alcohols, nucleotide precursors) and purification methods have not been conducted to establish when the sulfide form is preferentially applicable over existing phosphorylation agents.

• Gazania rigens (L.) gaertn leaf extract-inspired innovative synthesis of silver nanoparticles and promising applications as antibacterial and cytotoxic agents (2026) · doi

  The role of phytochemical coating composition from Gazania rigens leaf extract in mediating targeted accumulation of AgNPs has been proposed but not experimentally validated. The paper references that phytomolecules enhance biological compatibility and enable targeted accumulation via the external nanoparticle layer, yet does not provide chromatographic characterization of specific phytocompounds or structure-activity relationships between individual phytochemicals and cancer cell selectivity.

• Quinolines, a perpetual, multipurpose scaffold in medicinal chemistry (2021) · doi

  Quinoline-rhodamine hybrids showed antitubercular activity against Mycobacterium tuberculosis and Mycobacterium bovis, but no in vivo efficacy studies in animal tuberculosis models have been reported to validate the translation from in vitro antitubercular screening to systemic absorption and bioavailability in infected organisms.

• My journey in the CO2-chemistry wonderland (2017) · doi

  Metal oxide catalysts for selective epoxidation of olefins show unpredictable performance dependent on the 'mode of being' of the oxide on the catalyst surface, which varies with synthetic procedure and uncontrolled factors. Systematic characterization studies are needed to identify and control the surface oxide structure parameters that determine whether the catalyst produces selective epoxidation (100% propene oxide) versus combustion or aldehyde/ketone formation.

• Resonance-enhanced multiphoton ionization time-of-flight mass spectrometry for the real-time analysis of a retronasal aroma compound from a cumin sandwich (2026) · doi

  The proposed logistic function fitting approach for extracting quantitative release times (γ1, γ2) from time profiles exhibiting breath-synchronized fluctuations has not been validated against independent methods or on other aroma compound classes beyond p-cymene in cumin sandwiches using REMPI-TOFMS.

• Rocco Ungaro, 40 years of Calixarene chemistry (2016) · doi

  Glyco-calixarenes have been synthesized and shown to block cholera toxin and target galectins in cancer cell progression, but systematic quantitative binding affinity studies comparing different glycosylation patterns and carbohydrate multivalency arrangements with protein targets remain unreported.

• cAMPS derivatives. A minireview over synthetic medicinal chemistry (2019) · doi

  The paper notes that 8-halogeno cAMPS derivatives may undergo in vivo covalent bonding with heteronucleophiles such as cysteine thiols, potentially affecting biodata and toxicity profiles, but provides no experimental data quantifying these covalent adducts or their pharmacological consequences in cellular or animal models.

• Multicomponent reactions in crop protection chemistry (2020) · doi

  Multicomponent syntheses of mandipropamid-related mandelamides and oomyceticides using alkyne chemistry have been reported, but systematic comparison of different multicomponent reaction pathways (Kabachnik-Fields vs. isocyanide-based approaches) for generating these fungicide scaffolds has not been conducted.

• Basic Coordination Chemistry for Biologists (2019) · doi

  The spectrochemical series for ligands is explicitly stated to be built on experimental data for metal ions in common oxidation states, but the applicability of this series to uncommon oxidation states and metal ions beyond the transition series has not been systematically investigated. Clarification is needed on how the ligand field splitting ordering changes when applied to lanthanides, actinides, or high-valence transition metal complexes.