Migration Of Hydrogen Atom Research Articles

Combined Crossed Molecular Beams and Ab Initio Study of the Bimolecular Reaction of Ground State Atomic Silicon (Si; 3 P) with Germane (GeH4 ; X1 A1 ).

The chemical dynamics of the elementary reaction of ground state atomic silicon (Si; 3 P) with germane (GeH4 ; X1 A1 ) were unraveled in the gas phase under single collision condition at a collision energy of 11.8±0.3 kJ mol-1 exploiting the crossed molecular beams technique contemplated with electronic structure calculations. The reaction follows indirect scattering dynamics and is initiated through an initial barrierless insertion of the silicon atom into one of the four chemically equivalent germanium-hydrogen bonds forming a triplet collision complex (HSiGeH3 ; 3 i1). This intermediate underwent facile intersystem crossing (ISC) to the singlet surface (HSiGeH3 ; 1 i1). The latter isomerized via at least three hydrogen atom migrations involving exotic, hydrogen bridged reaction intermediates eventually leading to the H3 SiGeH isomer i5. This intermediate could undergo unimolecular decomposition yielding the dibridged butterfly-structured isomer 1 p1 (Si(μ-H2 )Ge) plus molecular hydrogen through a tight exit transition state. Alternatively, up to two subsequent hydrogen shifts to i6 and i7, followed by fragmentation of each of these intermediates, could also form 1 p1 (Si(μ-H2 )Ge) along with molecular hydrogen. The overall non-adiabatic reaction dynamics provide evidence on the existence of exotic dinuclear hydrides of main group XIV elements, whose carbon analog structures do not exist.

Efficient Electrochemical Water Splitting with PdSn4 Dirac Nodal Arc Semimetal

Recently, several researchers have claimed the existence of superior catalytic activity associated with topological materials belonging to the class of Dirac/Weyl semimetals, owing to the high electron conductivity and charge carrier mobility in these topological materials. By means of X-ray photoelectron spectroscopy, electrocatalytic tests, and density functional theory, we have investigated the chemical reactivity (chemisorption of ambient gases), ambient stability, and catalytic properties of PdSn4, a topological semimetal showing Dirac node arcs. We find a Tafel slope of 83 mV in the hydrogen evolution reaction (HER) dec–1 with an overpotential of 50 mV, with performances resembling those of pure Pd, regardless of its limited amount in the alloy, with a subsequent reduction in the cost of raw materials by ∼80%. Remarkably, the PdSn4-based electrode shows superior robustness to CO compared to pure Pd and Pt and high stability in water media, although the PdSn4 surface is prone to oxidation with the formation of a sub-nanometric SnO2 skin. Moreover, we also assessed the significance of the role of topological electronic states in the observed catalytic properties. Actually, the peculiar atomic structure of oxidized PdSn4 enables the migration of hydrogen atoms through the Sn–O layer with a barrier comparable with the energy cost of the Heyrovsky step of HER over Pt(111) in acidic media (0.1 eV). On the other hand, the topological properties play a minor role, if existing, contrarily to the recent reports overestimating their contribution in catalytic properties.

MEMS hydrogen gas sensor with wireless quartz crystal resonator

Abstract A highly sensitive hydrogen-gas sensor fabricated using MEMS technology is presented. The sensor chip consists of glass substrates, silicon substrate, and an AT-cut quartz crystal resonator, which is embedded in the microchannel constructed on the substrates. The quartz resonator has a fundamental resonant frequency of 165 MHz and a 200 nm palladium film deposited on its single surface as the hydrogen-gas sensing material. The MEMS hydrogen-gas sensor operates in a wireless manner by exciting and detecting the resonator vibration using the non-contacting antennas. The curvature induced resonant frequency change of the resonator plate caused by the expansion of the palladium film is used for the detection of the hydrogen gas. We succeeded in improving the hydrogen absorption rate and then the sensitivity for the hydrogen-gas detection by applying the air-plasma treatment method, and clarified the role of palladium oxide in lowering the energy barrier for the hydrogen-atom migration from surface to subsurface with the X-ray photoelectron spectroscopy. Thus sensitivity enhanced MEMS hydrogen-gas sensor exhibits a detection limit of 10 ppm or less at room temperature both in nitrogen and air.

Facilitating hydrogen atom migration via a dense phase on palladium islands to a surrounding silver surface

The migration of species across interfaces can crucially affect the performance of heterogeneous catalysts. A key concept in using bimetallic catalysts for hydrogenation is that the active metal supplies hydrogen atoms to the host metal, where selective hydrogenation can then occur. Herein, we demonstrate that, following dihydrogen dissociation on palladium islands, hydrogen atoms migrate from palladium to silver, to which they are generally less strongly bound. This migration is driven by the population of weakly bound states on the palladium at high hydrogen atom coverages which are nearly isoenergetic with binding sites on the silver. The rate of hydrogen atom migration depends on the palladium-silver interface length, with smaller palladium islands more efficiently supplying hydrogen atoms to the silver. This study demonstrates that hydrogen atoms can migrate from a more strongly binding metal to a more weakly binding surface under special conditions, such as high dihydrogen pressure.

Mechanisms of Acid-Promoted N2 and N2O Generation from NH2NO and NH2NO2

The effects of water, formic acid, and nitric acid on N2 and N2O generation from NH2NO and NH2NO2 are studied using high-level quantum-chemical calculations. It is shown that the reaction barriers from isolated NH2NO and NH2NO2 are 35.5 kcal/mol and 38.1 kcal/mol, respectively. When the NH2NO and NH2NO2 reactions are examined in the presence of water, formic acid, or nitric acid, the energy barriers are different. The mechanisms of these reactions are revealed through reaction pathway calculations. The isomerization of intermediate HNNOH and HNNOOH molecules, which follows a group rotation mechanism, plays a key role in reactions of isolated NH2NO and NH2NO2. However, the presence of water, formic acid, or nitric acid changes the isomerization mechanism substantially. HNNOH or HNNOOH and the catalyzing molecule form a doubly hydrogen bonded pre-reactive complex, which in turn facilities hydrogen atom migration (this is denoted as the hydrogen atom migration mechanism). This study demonstrates the feasibility of N2 and N2O generation from NH2NO or NH2NO2 in the presence of water, formic acid, or nitric acid.

New insights into the anti-disproportionation mechanism of ZrCo alloying with Ti, Hf, Sc, Cu, and Fe elements

First-principles calculations were performed to investigate the effects of alloying substitutions (i.e. Ti, Hf, Sc, Cu and Fe) on the anti-disproportionation ability of ZrCo alloy. For the first time, we revealed the disproportionation mechanism from the energy point of view and provided a new theoretical method to predict whether the substitution element has the ability to enhance the anti-disproportionation performance of ZrCo alloy. Based on the hydrogen atom occupancy behavior in ZrCoH3 and the results of our calculation of binding energy, the hydrogen atom migration model during hydrogenation and theoretical computational model were established. Through structural optimization, a series of stable 2 × 1 × 2 ZrCoH3 supercells were obtained, which contain four hydrogen atoms occupying 8e site and various substitution atoms with different amounts except for pure system. The binding energy of hydrogen atom in the 8e site and activation energy of diffusing from 8e site to 4c2 site of these ZrCoH3 supercells were calculated. The results showed that the substitution of Ti and Hf increased the binding energy of hydrogen atom in the 8e site, while the substitution of Fe, Cu and Sc decreased the binding energy of hydrogen atom in the 8e site. Meanwhile, both of Ti and Hf substitution reduced the activation energy of diffusing from 8e site to 4c2 site, while all of Fe, Cu and Sc substitution increased the activation energy of diffusing from 8e site to 4c2 site. These results indicated that hydrogen-induced disproportionation was the inherent property of ZrCo alloy, and element substitution can restrain or accelerate disproportionation by affecting both the binding energy and activation energy. With simultaneous consideration of the binding energy and activation energy, the effect of these alloying substitutions on the anti-disproportionation ability could be ascertained and the results were in good agreement with the previous theoretical and experimental results.

Reduction of Oxidized Pd/Ag(111) Surfaces by H2: Sensitivity to PdO Island Size and Dispersion

Understanding the migration of species across interfaces in bimetallic systems is key to exploiting their bifunctionality for chemical reactivity and heterogeneous catalysis. The present study demonstrates that the sizes and dispersion of oxidized Pd islands present on oxidized Ag(111) in addition to the concentration of active Pd sites have a significant influence on the rate of surface reduction by H2. Two distinct types of Pd oxide islands were generated for this investigation and characterized using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy. Small, uniformly dispersed PdOx islands (1–5 nm diameter) were created by depositing Pd onto AgOx surfaces, while larger, non-uniformly dispersed PdOx agglomerates (30–50 nm) were produced by depositing Pd on Ag(111) prior to oxidizing. Based on XPS, the small PdOx islands have a higher concentration of undercoordinated Pd atoms than the large agglomerates. Both types of PdOx are found to dramatically enhance the reduction of AgOx by H2 at 300 K due to the ability of PdOx to dissociate H2; the pure AgOx surfaces are unreactive toward H2. The rate of reduction at 300 K is found to be 2–4 times larger for the AgOx surface covered by small, uniformly dispersed PdOx islands. The higher reactivity of this surface is attributed to enhanced migration of oxygen and hydrogen atoms between the PdOx and AgOx phases due to the sizes and high dispersion of the small PdO islands as well as the higher concentration of active Pd sites on the PdOx domains. This study demonstrates that reactant migration between co-existing surface phases is highly sensitive to both the intrinsic chemical activity and morphological properties of the active phase (PdOx) and reveals that these properties can be significantly influenced by the method of synthesizing the oxidized bimetallic surfaces.

H migration in peroxy radicals under atmospheric conditions

Abstract. A large data set of rate coefficients for H migration in peroxy radicals is presented and supplemented with literature data to derive a structure–activity relationship (SAR) for the title reaction class. The SAR supports aliphatic RO2 radicals; unsaturated bonds and β-oxo substitutions both endocyclic and exocyclic to the transition state ring; and α-oxo (aldehyde), –OH, –OOH, and –ONO2 substitutions, including migration of O-based hydrogen atoms. Also discussed are –C(=O)OH and –OR substitutions. The SAR allows predictions of rate coefficients k(T) for a temperature range of 200 to 450 K, with migrations spans ranging from 1,4 to 1,9-H shifts depending on the functionalities. The performance of the SAR reflects the uncertainty of the underlying data, reproducing the scarce experimental data on average to a factor of 2 and the wide range of theoretical data to a factor of 10 to 100, depending also on the quality of the data. The SAR evaluation discusses the performance in multi-functionalized species. For aliphatic RO2, we also present some experimental product identification that validates the expected mechanisms. The proposed SAR is a valuable tool for mechanism development and experimental design and guides future theoretical work, which should allow for rapid improvements of the SAR in the future. Relative multi-conformer transition state theory (rel-MC-TST) kinetic theory is introduced as an aid for systematic kinetic studies.

Induced Fit of Crown Cavity to Ammonium Ion Guests and Photoinduced Intracavity Reactions: Cold Gas-Phase Spectroscopy of Dibenzo-18-Crown-6 Complexes with NH4+, CH3NH3+, and CH3CH2NH3.

Ultraviolet photodissociation (UVPD) spectra of dibenzo-18-crown-6 (DB18C6) complexes with NH4+, CH3NH3+ (MeNH3+), and CH3CH2NH3+ (EtNH3+) [NH4+(DB18C6), MeNH3+(DB18C6), and EtNH3+(DB18C6), respectively] were observed under cold gas-phase conditions. We also measured the infrared (IR)-UV double-resonance spectra of these complexes in the NH stretching region to examine the encapsulation structure. The UVPD and IR-UV spectra were analyzed using quantum chemical calculations. All the ammonium complexes show sharp 0-0 bands at positions close to that of the K+(DB18C6) complex; the conformation of the DB18C6 component in the ammonium complexes is similar to that in K+(DB18C6). In addition, the ammonium complexes each have another type of isomer that the K+(DB18C6) complex does not show in the gas phase. In these isomers, the conformation of the DB18C6 cavity changes, and the strength of the NH···O hydrogen bond increases. During the UVPD, the NH4+(DB18C6) complex provides various photofragment species, such as the C8H9O2+ ion, resulting from cleavage of the DB18C6 component, whereas the dominant fragment ion for the MeNH3+(DB18C6) and EtNH3+(DB18C6) complexes is the ammonium ion itself. The UVPD investigation of deuterated systems suggests that after UV excitation of the NH4+(DB18C6) complex, the dissociation process is initiated by proton transfer from NH4+ to DB18C6, followed by the migration of hydrogen atoms in the crown cavity and the cleavage of the ether ring.

Catalyst Surface Dispersion: Insights into Hydrogenation Kinetics and Mechanism

Catalyst-driven hydrogenation of an unsaturated organic matrix is commonly used for irreversible scavenging of hydrogen. The effect of catalyst dispersion on the hydrogenation reaction was explored as a means to deciphering the hydrogenation mechanism. The hydrogenation rate was thus measured in a model system consisting of a composite of a graphene nanoplatelet (GNP)-supported catalyst (Pd) in an organic matrix comprising the hydrogen scavenger 1,4-di(phenylethynyl)benzene (DEB). A similar activated carbon (AC)-supported Pd system in a DEB matrix was used as a reference system. We found that the rate of the hydrogenation reaction was limited by the migration of hydrogen atoms to the scavenger from the carbon-based catalyst support and could be manipulated by tuning (1) the specific surface area (SSA) of the catalyst support and (2) the mean catalyst-to-scavenger distance (catalyst dispersion quality) in the overall composite. We integrated these two key parameters into a single design parameter, termed the catalyst surface density (CSD). We found that for catalyst particles smaller than 100 nm the rate-determining step of the hydrogenation reaction was mainly dictated by the quality of the catalyst dispersion, expressed by the CSD parameter. Manipulating the CSD at a fixed composite composition yielded up to 7-fold acceleration in the hydrogenation rate, which is identical to the effect of increasing the concentration of the expensive and heavy catalyst by the same factor.

Defluoroalkylation of sp3 C−F Bonds of Industrially Relevant Hydrofluoroolefins

A simple, one-pot procedure is reported for the selective defluoroalkylation of trifluoromethyl alkene derivatives with aldehydes and ketones. The reaction sequence allows construction of a new C-C bond in a highly selective manner from a single sp3 C-F bond of a CF3 group in the presence of sp2 C-F bonds. The scope incorporates industrially relevant fluorocarbons including HFO-1234yf and HFO-1234ze. No catalyst, additives or transition metals are required, rather the methodology relies on a recently developed boron reagent. Remarkably, the boron site of this reagent plays a dual role in the reaction sequence, being nucleophilic at boron in the C-F cleavage step (SN 2') but electrophilic at boron en route to the carbon-carbon bond-forming step (SE 2'). The duplicitous behaviour is underpinned by a hydrogen atom migration from boron to the carbon atom of a carbene ligand.

Icosahedral Carborane Superacids and their Conjugate Bases Comprising H, F, Cl, and CN Substituents: A Theoretical Investigation of Monomeric and Dimeric Cages.

Theoretical investigation of the H(CHB11 X11 ) (X=H, F, Cl, CN), H(CHB11 Xn Y11-n ) (X,Y=F, Cl; n=1,5), and dimeric (H(CHB11 X11 ))2 (X=F, Cl) carborane superacids performed at the B3LYP/6-311++G(d,p) theory level revealed the similarity of their equilibrium structures and the possibility of nearly barrierless hydrogen atom migration among the substituents attached to one side of the icosahedral CB11 cage. The vertical electron detachment energies predicted at the OVGF/6-311++G(3df,2pd) theory level for the conjugate bases (CHB11 X11 )- were found to span the 5.82-9.00 ev range. The acid strengths (manifested by the Gibbs free deprotonation energies spanning the 213-266 kcal/mol range) predicted for the icosahedral H(CHB11 X11 ) carborane systems confirm their superacidic properties which might be increased even further by the attachment of the second carborane H(CHB11 X11 ) unit that leads to a dimeric structure mimicking a part of an experimentally observed H-bridged polymeric chain. The Gibbs free deprotonation energy of the dimeric (H(CHB11 Cl11 ))2 acid was predicted to be smaller by 17 kcal/mol than that of the corresponding monomeric H(CHB11 Cl11 ) acid.

Guanine-adenine interactions in DNA tetranucleotide cation radicals revealed by UV/vis photodissociation action spectroscopy and theory.

Hydrogen-rich cation radicals (GATT + 2H)+˙ and (AGTT + 2H)+˙ represent oligonucleotide models of charged hydrogen atom adducts to DNA. These tetranucleotide cation radicals were generated in the gas phase by one-electron reduction of the respective (GATT + 2H)2+ and (AGTT + 2H)2+ dications in which the charging protons were placed on the guanine and adenine nucleobases. We used wavelength-dependent UV/Vis photodissociation in the valence-electron excitation region of 210-700 nm to produce action spectra of (GATT + 2H)+˙ and (AGTT + 2H)+˙ that showed radical-associated absorption bands in the near-UV (330 nm) and visible (400-440 nm) regions. Born-Oppenheimer molecular dynamics and density-functional theory calculations were used to obtain and rank by energy multiple (GATT + 2H) dication and cation-radical structures. Time-dependent density functional theory (TD-DFT) calculations of excited-state energies and electronic transitions in (GATT + 2H)+˙ were augmented by vibronic spectra calculations at 310 K for selected low-energy cation radicals to provide a match with the action spectrum. The stable product of one-electron reduction was identified as having a 7,8-dihydroguanine cation radical moiety, formed by intramolecular hydrogen atom migration from adenine N-1-H. The hydrogen migration was calculated to have a transition state with a low activation energy, Ea = 96.5 kJ mol-1, and positive activation entropy, ΔS‡ = 75 J mol-1 K-1. This allowed for a fast isomerization of the primary reduction products on the ion-trap time scale of 150 ms that was substantially accelerated by highly exothermic electron transfer.

Hydrogenation, dehydrogenation of α-tetragonal boron and its transition to δ-orthorhombic boron

Boron bulk crystals are marked by exceptional structural complexity and unusual related physical phenomena. Recent reports of hydrogenated α-tetragonal and a new δ-orthorhombic boron B52 phase have raised many fundamental questions. Using density functional theory calculations it is shown that hydrogenated α-tetragonal boron has at least two stable stoichiometric compositions, B51H7 and B51H3. Thermodynamic modeling was used to qualitatively reproduce the two-step phase transition reported by (Ekimov et al 2016 J. Mater. Res. 31, 2773) upon annealing, which corresponds to successive transitions from B51H7 to B51H3 to pure B52. The so obtained δ-orthorhombic boron is an ordered, low-temperature phase and α-tetragonal boron is a disordered, high-temperature phase of B52. The two phases are connected by an order-disorder transition, that is associated with the migration of interstitial boron atoms. Atom migration is usually suppressed in strongly bound, covalent crystals. It is shown that the migration of boron atoms is likely to be assisted by the migration of hydrogen atoms upon annealing. These results are in excellent agreement with the above mentioned experiment and they represent an important step forward for the understanding of boron and hydrogenated boron crystals. They further open a new avenue to control or remove the intrinsic defects of covalently bound crystals by utilizing volatile, foreign atoms.

The theoretical studies on the adsorption and migration of hydrogen atom on the two-dimensional nanocrystal surface

An analytical model is presented to study the adsorption and migration of atoms/ions on the surface of two-dimensional nanocrystal. An atom/ion interacts with every atom of the two-dimensional nanocrystal through a pairwise potential which can be approximated by the Lennard-Jones (L-J) potential. Using the Fourier expansion of the interaction potential, the total interaction energy between the adsorption atom/ion and the two-dimensional nanocrystal is derived. Adsorption energy and adsorption stability of a hydrogen atom are analyzed on three special sites for three kinds of typical crystal surfaces. The interaction potential of the hydrogen atom migrating along specific paths on the surface of three kinds of typical nanocrystals is illustrated and analyzed.

Photoinduced reversible isomerization of 9H-fluorene into 1H-fluorene by means of hydrogen-atom migration and the lowest electronically excited triplet state studied by matrix-isolation FTIR spectroscopy

Photoinduced reversible intramolecular hydrogen-atom migration between 9H-fluorene and 1H-fluorene isolated in an Ar matrix is found by FTIR spectroscopy with an aid of DFT calculation. The forward isomerization from 9H-fluorene to 1H-fluorene occurs upon UV irradiation (λ ≥ 295 nm), while the backward isomerization occurs upon λ ≥ 320 nm light irradiation. The less stable isomer, 1H-fluorene, is identified by comparison of the measured IR spectrum with the corresponding simulated spectral pattern obtained at the B3LYP/6-31++G(d,p) level. In addition, an IR spectrum of 9H-fluorene in the T1 state is measured during UV irradiation (λ ≥ 275 nm).

Theoretical analysis of the adsorption of ammonia–borane and their dehydrogenation products on the (001) surface of TiC and ZrC

The adsorption of ammonia–borane (AB) over the (001) surface of TiC and ZrC, has been studied systematically by means of periodic-boundary density functional calculations using slab models. We present evidence that a surface with an appreciable degree of polarity such as those used in this research, can simultaneously activate the N-H and B-H bonds of the AB molecule and its dimer AB-AB. The molecule is highly activated by both supports, and the N-H and B-H bonds are stretched long enough to release one or two hydrogens. Additionally, the bond distance B-N is shortened by 0.04 and 0.06 Å by TiC and ZrC supports respectively, which results in the strengthening of the bond, what seems convenient to avoid unwanted by-products (NH3, BH3, etc.). A systematic study for the adsorption of BH2NH2, which is isoelectronic with ethylene, was also done. The adsorption leads to a major elongation of the B-N bond with respect to the calculated value in the gas phase (0.17 and 0.18 Å for TiC and ZrC respectively). Both supports can activate the molecule, with the biggest impact being on the BH2 fragment. On the other hand, the migration of hydrogen atoms on both supports is a thermodynamically favorable process. On the surface H prefers bonding to a C, which is in agreement with other studies for dissociative adsorption of H2 on metallic carbides. Nevertheless, we show that the hydrogen molecule readily forms when both atoms sit on the transition metal of the surface. On the basis of this theoretical study, both supports are proposed as potential catalysts for the dehydrogenation of ammonia–borane.

Red-light induced photoreaction of ozone-dimethylamine complex; matrix-isolation infrared spectra of dimethylamine-N-oxide and N,N-dimethylhydroxylamine

Photoreaction of molecular complex composed of ozone and dimethylamine is investigated by matrix-isolation IR and UV–visible spectroscopies. The UV–visible spectrum of the molecular complex isolated in an Ar matrix shows two broad bands in the region between 400 and 700 nm. Upon red-light irradiation (λ ≥ 680 nm), dimethylamine-N-oxide is produced by intermolecular oxygen-atom transfer from O3 to the lone pair on the nitrogen atom of dimethylamine. Dimethylamine-N-oxide isomerizes to N,N-dimethylhydroxylamine by intramolecular hydrogen-atom migration upon the second light irradiation (λ ≥ 385 nm). The both photoproducts are identified by the DFT calculation at the B3LYP/6-31++G(d,p) level.

Spontaneous Isomerization of Peptide Cation Radicals Following Electron Transfer Dissociation Revealed by UV-Vis Photodissociation Action Spectroscopy.

Peptide cation radicals of the z-type were produced by electron transfer dissociation (ETD) of peptide dications and studied by UV-Vis photodissociation (UVPD) action spectroscopy. Cation radicals containing the Asp (D), Asn (N), Glu (E), and Gln (Q) residues were found to spontaneously isomerize by hydrogen atom migrations upon ETD. Canonical N-terminal [z4 + H]+● fragment ion-radicals of the R-C●H-CONH- type, initially formed by N-Cα bond cleavage, were found to be minor components of the stable ion fraction. Vibronically broadened UV-Vis absorption spectra were calculated by time-dependent density functional theory for several [●DAAR + H]+ isomers and used to assign structures to the action spectra. The potential energy surface of [●DAAR + H]+ isomers was mapped by ab initio and density functional theory calculations that revealed multiple isomerization pathways by hydrogen atom migrations. The transition-state energies for the isomerizations were found to be lower than the dissociation thresholds, accounting for the isomerization in non-dissociating ions. The facile isomerization in [●XAAR + H]+ ions (X = D, N, E, and Q) was attributed to low-energy intermediates having the radical defect in the side chain that can promote hydrogen migration along backbone Cα positions. A similar side-chain mediated mechanism is suggested for the facile intermolecular hydrogen migration between the c- and [z + H]●-ETD fragments containing Asp, Asn, Glu, and Gln residues. Graphical Abstract ᅟ.

Tertiary-Alcohol-Directed Functionalization of Remote C(sp3 )-H Bonds by Sequential Hydrogen Atom and Heteroaryl Migrations.

Reported for the first time is a tertiary-alcohol-guided heteroarylation of remote C(sp3 )-H bonds. The mild and direct generation of alkoxyl radicals from alcohols is enabled by visible-light photocatalysis. A remote hydrogen atom and heteroaryl migration sequence are involved in the reaction. Many sensitive groups remain intact in the reaction, thus illustrating wide functional-group compatibility. This protocol provides a practical strategy for the late-stage modification of alkyl ketones.