scholarly journals A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

2022 ◽  
Author(s):  
Cynthia Melendrez ◽  
Jorge Lopez-Rosas ◽  
Camron Stokes ◽  
Tsz Cheung ◽  
Sang-Jun Lee ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Chemical Reactivity ◽  
Bond Formation ◽  
Covalent Bond ◽  
Diamond Lattice ◽  
Diamond Surface ◽  
Chemical Transformations ◽  
Alkyl Bromide ◽  
Sensing Applications

Bromination of high-pressure high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming and most researchers simply use oxygen-terminated ND (alcohols and acids) as a reactive species. In this work, we transformed a tertiary alcohol-rich ND surface to an amine surface with 50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl-bromide moieties are highly labile on NDs and are metastable as previously found using density functional theory. The instability of the bromine terminated ND is explained by steric hindrance and poor surface energy stabilization. The strong leaving group properties of the alkyl-bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. The chemical lability of the brominated ND surface led to efficient amination with NH3•THF at 298 K, and a catalyst-free Sonogashira-type reaction with an alkyne-amine produced an 11-fold increase in amination rate. Overlapping spectroscopies under inert, temperature-dependent and open-air conditions provided unambiguous chemical assignments. Amine-terminated NDs and folic acid were conjugated using sulfo-NHS/EDC coupling reagents to form amide bonds, confirming that standard amine chemistry remains viable. This work supports that a robust pathway exists to activate a chemically inert diamond surface at room temperature, which broadens the pathways of bond formation when a reactive alkyl-bromide surface is prepared. The unique surface properties of brominated and aminated nanodiamond reported here are impactful to researchers who wish to chemically tune diamond for quantum sensing applications or as an electron source for chemical transformations.

scholarly journals The synthesis of lysylfluoromethanes and their properties as inhibitors of trypsin, plasmin and cathepsin B

1987 ◽  
Vol 241 (3) ◽  
pp. 871-875 ◽  
Author(s):  
H Angliker ◽  
P Wikstrom ◽  
P Rauber ◽  
E Shaw
Keyword(s):  
Proximity Effect ◽  
Cathepsin B ◽  
Chemical Reactivity ◽  
Bond Formation ◽  
Synthesis Method ◽  
Covalent Bond ◽  
Active Centre ◽  
Fluoro Derivative ◽  
Order Of Magnitude ◽  
Covalent Bond Formation

The synthesis of two lysylfluoromethanes is described by an extension of the synthesis method of Rauber, Angliker, Walker & Shaw [(1986) Biochem. J. 239, 633-640]. Ala-Phe-Lys-CH2F was found to be an active-centre-directed inhibitor of plasmin and trypsin, as is the corresponding chloromethane. However, the rate of covalent-bond formation is about an order of magnitude lower at 25 degrees C for the fluoro derivative. It was, in addition, an extremely effective inactivator of cathepsin B at pH 5.4 and 6.4. The chemical reactivity of fluoromethanes was compared with that of chloromethanes as alkylators of GSH. At pH 7.4 and 37 degrees C, a fluoromethane has 1/500th the reactivity of a chloromethane. A comparison of the rates of reaction of the fluoromethane with cathepsin B and with GSH at pH 6.4 revealed an enhancement of 10(8)-fold for the alkylation of the enzyme, ascribable largely to a proximity effect.

Covalent Bond Formation in Defected Nanopeapods Induces Local Deformations on Nanotube Walls

2006 ◽  
Vol 963 ◽  
Author(s):  
Takashi Yumura ◽  
Miklos Kertesz
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional Theory ◽  
Carbon Nanotube ◽  
Dft Calculations ◽  
Density Functional ◽  
Bond Formation ◽  
Covalent Bond ◽  
Functional Theory ◽  
Single Walled Carbon Nanotube ◽  
Covalent Bond Formation

ABSTRACTProperties of defected nanopeapods, in which a defected C60 cage with a C1–C59 topology is encapsulated inside a (10,10) single walled carbon nanotube, have been analyzed using density functional theory (DFT) calculations. When new CC bonds are formed between the defected C60 and the nanotube, the CC network of the nanotube is perturbed near the binding site, and has butadiene and quinonoid perturbations. Such geometrical changes could play an important role in the selective functionalizations of carbon nanotubes.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

Recent Advances on C-Se Bond-forming Reactions at Low and Room Temperature

2020 ◽  
Vol 23 (28) ◽  
pp. 3206-3225 ◽  
Author(s):  
Amol D. Sonawane ◽  
Mamoru Koketsu
Keyword(s):  
Room Temperature ◽  
Bond Formation ◽  
Bond Forming ◽  
Material Chemistry ◽  
Recent Advances ◽  
Bond Forming Reactions ◽  
Bond Formation Reactions

: Over the last decades, many methods have been reported for the synthesis of selenium- heterocyclic scaffolds because of their interesting reactivities and applications in the medicinal as well as in the material chemistry. This review describes the recent numerous useful methodologies on C-Se bond formation reactions which were basically carried out at low and room temperature.

Isolation of Natural Compounds from Syzygium densiflorum Fruits and Exploring its Chemical Property, Therapeutic Role in Diabetic Management

2020 ◽  
Vol 10 (2) ◽  
pp. 168-176
Author(s):  
Krishnasamy Gopinath ◽  
Nagarajan Subbiah ◽  
Muthusamy Karthikeyan
Keyword(s):  
Density Functional ◽  
Chemical Reactivity ◽  
Natural Compounds ◽  
Structure Activity Relationship ◽  
Activity Relationship ◽  
Computational Studies ◽  
Therapeutic Role ◽  
Relationship Analysis ◽  
Structure Activity

Background: Syzygium densiflorum Wall. ex Wight & Arn (Myrtaceae) has been traditionally used by the local tribes of the Nilgiris, Tamil Nadu, India, for the treatment of diabetes. Objective: This study aimed to isolate the major phytoconstituents from the S. densiflorum fruits and to perform computational studies for chemical reactivity and biological activity of the isolated compound. Materials and Methods: Two different compounds were isolated from ethanolic extract of S. densiflorum fruits and purified using HPLC. The structures of the compounds were elucidated on the basis of their 1H NMR, 13C NMR, 1H-1H COSY, HMBC, HRESIMS, and FT-IR data. Further, the chemical reactivity of the compounds was analyzed by density functional theory calculations and its therapeutic role in diabetic management was examined by comparing the structure of isolated compounds with previously reported bioactive compounds. Results: Of the two compounds ((6,6 & 1-kestopentaose (1) and 6-(hydroxymethyl)-3-[3,4,5- trihydroxy- 6-[(3,4,5-trihydroxyoxan-2-yl)oxymethyl]oxan-2-yl]oxyoxane-2,4,5-triol)(2)). β-glucosidase, β-galactosidase, α-glucosidase and β-amylase inhibition activity of the compounds were predicted by structure activity relationship. Conclusion: Structure-activity relationship analysis was performed to predict the therapeutic role of isolated compounds. These computational studies may be performed to minimize the efforts to determine the therapeutic role of natural compounds.

Reactions of macroions with ester and carboxylic groups of polymers

1987 ◽  
Vol 52 (9) ◽  
pp. 2194-2203
Author(s):  
Miloslav Kučera ◽  
Dušan Kimmer ◽  
Karla Majerová ◽  
Josef Majer
Keyword(s):  
Maleic Anhydride ◽  
Acrylic Acid ◽  
Methyl Methacrylate ◽  
Bond Formation ◽  
Covalent Bond ◽  
The Other ◽  
Poly Methyl Methacrylate ◽  
Other Hand ◽  
Carboxylic Groups ◽  
Poly Acrylic Acid

In the reaction of dianions with poly(methyl methacrylate), only an insignificant amount of insoluble crosslinked product is obtained. If, however, the concentration of grafting dianions approaches that of ester groups, the amount of poly(methyl methacrylate) which may thus be crosslinked becomes quite significant. Dications, too, can bring about crosslinking of only an insignificant number of poly(methyl methacrylate) chains. Carboxylic groups in poly(acrylic acid) react with dianions and dications in an anhydrous medium similarly to ester groups. On the other hand, in the presence of a cocatalytic amount of water dications are more readily bound to carboxylic groups, forming a covalent bond. The relatively highest efficiency was observed in the bond formation between dication and the poly[styrene-alt-(maleic anhydride)], both in an anhydrous medium and in the presence of H2O.

scholarly journals Role of Chemistry and Crystal Structure on the Electronic Defect States in Cs-Based Halide Perovskites

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1032
Author(s):  
Anirban Naskar ◽  
Rabi Khanal ◽  
Samrat Choudhury
Keyword(s):  
Crystal Structure ◽  
Density Functional ◽  
Covalent Bond ◽  
Density Functional Theory Calculations ◽  
Antisite Defect ◽  
Defect States ◽  
Functional Theory ◽  
Electronic Defect ◽  
Constituent Elements

The electronic structure of a series perovskites ABX3 (A = Cs; B = Ca, Sr, and Ba; X = F, Cl, Br, and I) in the presence and absence of antisite defect XB were systematically investigated based on density-functional-theory calculations. Both cubic and orthorhombic perovskites were considered. It was observed that for certain perovskite compositions and crystal structure, presence of antisite point defect leads to the formation of electronic defect state(s) within the band gap. We showed that both the type of electronic defect states and their individual energy level location within the bandgap can be predicted based on easily available intrinsic properties of the constituent elements, such as the bond-dissociation energy of the B–X and X–X bond, the X–X covalent bond length, and the atomic size of halide (X) as well as structural characteristic such as B–X–B bond angle. Overall, this work provides a science-based generic principle to design the electronic states within the band structure in Cs-based perovskites in presence of point defects such as antisite defect.

scholarly journals Transforming Pt-SnO2 Nanoparticles into Pt-SnO2 Composite Nanoceramics for Room-Temperature Hydrogen-Sensing Applications

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2123
Author(s):  
Ming Liu ◽  
Caochuang Wang ◽  
Pengcheng Li ◽  
Liang Cheng ◽  
Yongming Hu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Sintering Temperature ◽  
Sno2 Nanoparticles ◽  
Hydrogen Sensing ◽  
Sensing Applications ◽  
Nanostructured Metal Oxides ◽  
Low Dimensional ◽  
Sensing Characteristics ◽  
Nanostructured Metal

Many low-dimensional nanostructured metal oxides (MOXs) with impressive room-temperature gas-sensing characteristics have been synthesized, yet transforming them into relatively robust bulk materials has been quite neglected. Pt-decorated SnO2 nanoparticles with 0.25–2.5 wt% Pt were prepared, and highly attractive room-temperature hydrogen-sensing characteristics were observed for them all through pressing them into pellets. Some pressed pellets were further sintered over a wide temperature range of 600–1200 °C. Though the room-temperature hydrogen-sensing characteristics were greatly degraded in many samples after sintering, those samples with 0.25 wt% Pt and sintered at 800 °C exhibited impressive room-temperature hydrogen-sensing characteristics comparable to those of their counterparts of as-pressed pellets. The variation of room-temperature hydrogen-sensing characteristics among the samples was explained by the facts that the connectivity between SnO2 grains increases with increasing sintering temperature, and Pt promotes oxidation of SnO2 at high temperatures. These results clearly demonstrate that some low-dimensional MOX nanocrystals can be successfully transformed into bulk MOXs with improved robustness and comparable room-temperature gas-sensing characteristics.

Sign in / Sign up

Export Citation Format

Share Document