Acetyl Halides Research Articles

Rapid Dissolution of Gold in Alcohols by In-Situ Generation of Halogens.

The dissolution of elemental gold is a fundamental step in its recycling by hydrometallurgy but has a significant environmental impact due to the use of strong acids or highly toxic reagents. Herein, it is shown that mixtures of acetyl halides and hydrogen peroxide in alcohols promote the rapid room-temperature dissolution of gold by halogenation to form Au(III) metalates. After leaching, distillation of the alcohol and re-dissolution in dilute HCl, the gold was refined through its precipitation by a simple diamide ligand; this method was also applied to separate gold from a mixture of metals. The leaching process is rapid, avoids the use of highly toxic materials and corrosive acids, and can be integrated into selective separation processes, so has the potential to be used in the purification of gold from ores, spent catalysts, and electronic and nano-waste.

Tuning Molecular Solar Thermal Properties by Modification of a Promising Norbornadiene Photoswitch

Carefully targeted modifications to the norbornadiene‐quadricyclane couple should give molecules with great potential for solar energy storage. Here we report the synthesis of derivatives of a well‐studied compound, 2‐cyano‐3‐anisyl norbornadiene (NBD5). The conjugation was extended by conversion of the nitrile into acrylonitrile and acrylate derivatives over two steps. Despite red‐shifting the absorbance properties, the metastable quadricyclanes exhibited extremely short lifetimes. Meanwhile, treatment of NBD5 with acetyl halides in the presence of aluminum trihalides led to the formation of 7‐acetyl norbornenes through a Wagner–Meerwein rearrangement. Subsequent transformations made it possible to synthesise norbornadienes with varying degrees of steric bulk at the 7‐position of the molecular scaffold. It was found that the bulkier this group was, the more stable the quadricyclane form. This reaction sequence allows for the synthesis of norbornadiene derivatives which are more suited to molecular solar thermal applications in domestic heating despite providing a slightly lower energy density.

Anomalous proton spin‐lattice relaxation in organic compounds containing methyl groups

AbstractTemperature measurements of proton spin‐lattice relaxation time performed for acetates ((CH3COO)2Ba, (CH3COO)2Cd, and (CH3COO)2Ca) and acetyl halides ((CH3CO)2O, CH3COBr and CH3COCl) are fitted to a Haupt equation. It is impossible to fit the temperature dependence of T1 protons using the BPP equation. Of importance is the assumption that complex C3 molecular motion of methyl protons takes place. An understanding of the correlation functions of complex C3 reorientation allow for the calculation of the relaxation time, T1, and the second moment of the NMR resonance. The spectral densities are calculated applying Woessner theory of complex motion and assuming a tunneling correlation time implemented from solving the Schrödinger equation. The acceptance of the tunneling correlation time resulting from the Schrödinger equation elucidates the reduction in the second moment at 0 K. The fitting leads to an excellent agreement between the experimental results of T1 temperature dependences and theoretical equations. From this, the tunneling splitting and motional parameters of methyl groups were estimated. The highest value of T1 minimum in the temperature dependence for (CH3COO)2Ba indicates the highest value of tunneling splitting. The smallest value, which is close to the T1 minimum value predicted by the BPP theory for CH3COCl, shows a lack or significantly reduced tunneling splitting. The tunneling jumps disappear at Ttun temperature, which was estimated for all studied compounds. The limitations on the use of Haupt's equation are presented. The presented approach differs from the other theoretical approaches and these differences are evaluated.

A theoretical study on the photodissociation mechanism of acetyl fluoride (CH3C(O)F) involving S0, S1, and T1 states

The dissociation potential energy surfaces of acetyl fluoride (CH3C(O)F) in the lowest three electronic states (S0, S1, and T1) have been calculated at the CASPT2-f12/VTZ-f12 level of theory. Combining with the surface intersection points, four mechanistic channels have been elucidated, namely, intersystem crossing (ISC) to the T1 state, internal conversion (IC) to the ground state, H-atom transfer, and direct dissociation along the S1 pathway. Unlike other acetyl halides, it is found that the α-CC bond cleavage in T1 surface after ISC to yield ground-state products CH3(2A′)+COF(2A′) is the most probable mechanism upon the excitation at 248nm, which agrees well with the experimental observation. Both the S1 and T1 potential energy surfaces are reported systematically for the first time. A comparison of the reactivity among CH3C(O)F, CH3C(O)Cl, CH3C(O)Br, CH3C(O)I and CH3C(O)CH3 has been made.

ChemInform Abstract: Regulation of Nonadiabatic Processes in the Photolysis of Some Carbonyl Compounds

AbstractReview: 83 refs.

ChemInform Abstract: Iron(III)‐Catalyzed Cycloisomerizations of Acetal—Vinylidenecyclopropanes: An Efficient Synthetic Route to 1,2‐Disubstituted Cyclobutenes.

AbstractThe Fe‐catalyzed cycloisomerization of vinylidenecyclopropanes in the presence of acetyl halide leads to 1,2‐disubstituted cyclobutenes such as (II)/(III), (V)/(VI), and (IX)/(X).

Regulation of nonadiabatic processes in the photolysis of some carbonyl compounds.

Carbonyl compounds studied are confined to acetyl halide (CH3COCl), acetyl cyanide (CH3COCN), acetyl sulfide (CH3COSH), acetaldehyde (CH3CHO), and methyl formate (HCOOCH3). They are asymmetrically substituted, but do not follow the well-known Norrish type I reactions. Each compound ejected in an effusive beam at about 300 K is commonly excited to the (1)(n, π*)CO lower state; that is, a nonbonding electron on O of the C[double bond, length as m-dash]O group is promoted to the antibonding orbital of π*CO. The photolysis experiments are conducted in the presence of Ar gas and the corresponding fragments are detected using time-resolved Fourier-transform Infrared (FTIR) emission spectroscopy. The enhancement of the collision-induced internal conversion or intersystem crossing facilitates the dissociation channels via highly vibrational states of the ground singlet (So) or triplet (T1) potential energy surfaces. In this manner, an alternative nonadiabatic channel is likely to open yielding different products, even if the diabatic coupling strength is strong between the excited state and the neighboring state. For instance, the photodissociation of CH3COCl at 248 nm produces HCl, CO, and CH2 fragments, in contrast to the supersonic jet experiments showing dominance of the Cl fragment eliminated from the excited state. If the diabatic coupling strength is weak, dissociation proceeds mainly through internal conversion, such as the cases of CH3COCN and CH3COSH. The photodissociation of CH3COCN at 308 nm has never been reported before, while for CH3COSH matrix-isolated photodissociation was conducted that shows a distinct spectral feature from the current FTIR method. The CH3CHO and HCOOCH3 molecules belong to the same type of carbonyl compounds, in which the molecular products, CO + CH4 and CO + CH3OH, are produced through both transition state and roaming pathways. Their products are characterized differently between molecular beam and current FTIR experiments. For instance, the photodissociation of HCOOCH3 at 248 nm yields CO with the vibrational state v ≥ 4, in contrast to the molecular beam experiments producing CO at v = 1. The photodissociation of CH3CHO at 308 nm intensifies a low energy component in the CH4 vibrational distribution, thus verifying the transition state pathway for the first time.

Adsorption of acetyl halide molecules on the surface of pristine and Al-doped graphene: Ab initio study

We have scrutinized the adsorption energy, electronic structure, natural bond analysis (NBO), density of state (DOS) and global indices for adsorption of acetyl chloride (AC) and acetyl fluoride (AF) on the surface of pristine graphene as well as Al-doped graphene. The adsorption energies have been calculated for the most stable configurations of the molecules on the surface of pristine and Al-doped graphene. According to the calculated parameters, there is very weak physical adsorption of AC and AF on pristine graphene while strong adsorption takes place in the case of Al-doped graphene. The charge transfer from adsorbed molecules to Al-doped graphene surface was confirmed by the natural bond orbital as well as the Mulliken population analysis while there is no charge transfer with pristine graphene. Additionally, the density of states results reveal that orbital hybridization takes place between above-mentioned molecules and Al-doped graphene sheet, whereas there is no hybridization between the molecules and the pristine graphene. Our calculated adsorption energies for the most stable position configurations of AC and AF on Al-doped graphene were −68.8kJmol−1 (−52.6kJmol−1 BSSE corrected energy) and −78.4kJmol−1 (−64.3kJmol−1 BSSE corrected energy) which are correspond to chemisorptions process respectively. These results point to the appropriateness of Al-doped graphene as a powerful adsorbent for practical applications.

Comparative Studies on the Reactions of Acetyl and Thioacetyl Halides with NH3 in the Gas Phase and in Aqueous Solution: A Theoretical Study

The reactions of acetyl halides, CH3C(═ O)X and corresponding sulfur analogues, thioacetyl halides, CH3C(=S)X, where X = F and Cl, with NH3 nucleophile were studied theoretically, at the QCISD level of theory, in the gas phase and in aqueous solution. All reactions occurred via the tetrahedral species, and reactions through neutral intermediates both in the gas phase and in aqueous solution could be ruled out, except for the case of the gas-phase reaction of acetyl fluoride. The tetrahedral structure was a transition state (TS) in the reactions of acetyl chloride, while it was a stable intermediate in reactions of thioacetyl halides. These differences could be caused by the π-bond strength of C ═ O and C ═ S. In the case of acetyl fluoride, the T(±)-type species was neither a saddle point nor an energy minimum in the gas phase, but existed as a stable intermediate in aqueous solution due to solvation. Moreover, in reactions of thioacetyl chloride, the rate-limiting step changed from the first step in the gas phase to the second step in aqueous solution, since the zwitterionic intermediates become more stabilized in aqueous solution. However, lower activation energies (ΔG(‡)) in aqueous solution were not caused by the solvent effects, but smaller deformation effects, in going from reactants through the TS.

ChemInform Abstract: Halogenative Allylation and Reduction of Aromatic Acetals by Double Substitution of Alkoxyl Groups in Acetal.

In the presence of excessive amount of acetyl halide along with a catalytic amount of tin(II) halide, aromatic acetals react with allyltrimethylsilane or triethylsilane to give α-allylbenzyl halides or benzyl halides, respectively, in good to excellent yields.

Theoretical problems associated with the use of acetic anhydride as a co-solvent for the non-aqueous titration of hydrohalides of organic bases and quaternary ammonium salts

A potentiometric titration study of organic base hydrohalides and quaternary ammonium salts using perchloric acid as the titrant and a mixture of acetic anhydride and acetic acid as the solvent was carried out and the titration mixture was analysed by NMR in order to clarify the chemistry of the reactions involved. It was found that in contrast to the general belief the formation of acetyl halides and titratable free acetate ion does not take place prior to the titration but NMR spectra proved the formation of acetyl halides in the course of the titration. This observation and the fact that the shape of the titration curves depends on the nature of the hydrohaloic acid bound to the base or of the anion in the quaternary ammonium salts led to the conclusion that the titrating agent is acetyl perchlorate formed in situ during the titration. Equations of the reactions involved in the titration process are shown in the paper.

The chemistry of niobium and tantalum halides, MX 5, with haloacetic acids and their related anhydrides: Anhydride C–H bond activation promoted by MF 5

Niobium and tantalum pentahalides, MX 5 ( 1), react with acetic acid and halo-substituted acetic acids, in 1:1 ratio, to give the dinuclear complexes [MX 4(μ-OOCMe)] 2 [M = Nb, X = Cl, 2a; M = Ta, X = Cl, 2b; Br, 2c] and [MCl 4(μ-OOCR)] 2 [M = Nb, R = CH 2Cl, 4a; CHCl 2, 4c; CCl 3, 4e; CF 3, 4g; CHBr 2, 4i; CH 2I, 4j; M = Ta, R = CH 2Cl, 4b; CHCl 2, 4d; CCl 3, 4f; CF 3, 4h]. The solid state structures of 2b and 4e have been ascertained by X-ray diffraction studies. The reactions of 1 with acetic anhydride and halo-substituted acetic anhydrides result in C–O bond activation and afford 2 and 4, respectively, with concomitant formation of acetyl halides. Moreover, the complexes MCl 5[OC(Cl)Me] [M = Nb, 3a; M = Ta, 3b] have been detected in significant amounts within the mixtures of the reactions of MCl 5 with acetic anhydride. TaI 5 is unreactive, at room temperature, towards both MeCOOH and (MeCO) 2O. MF 5 react with RCOOH (R = Me, CH 2Cl) in 1:1 molar ratio, to afford the ionic compounds [MF 4(RCOOH) 2][MF 6], 5a– d, in high yields. The additions of (RCO) 2O (R = Me, CH 2Cl) to MF 5 give 5, suggesting that anhydride C–H and C–O bonds activation is operative during the course of these reactions.

ChemInform Abstract: A Novel One‐Pot Conversion of Allyl Alcohols into Primary Allyl Halides Mediated by Acetyl Halide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Acetyl Halide Initiator Screening for the Cationic Ring‐Opening Polymerization of 2‐Ethyl‐2‐Oxazoline

AbstractKinetic investigations on the cationic ring‐opening polymerization of 2‐ethyl‐2‐oxazoline were conducted using acetyl chloride, acetyl bromide, and acetyl iodide as initiators. Various polymerization temperatures ranging from 80 to 220 °C were applied under microwave irradiation. The resulting polymerization mixtures were characterized with GC and GPC for the determination of monomer conversion and molecular weight distribution, respectively. Well defined polymers with narrow molecular weight distributions ($\overline M _{{\rm n,GPC}}$ = 6 000 Dalton, PDI ≈ 1.10) were obtained with all three initiators.magnified image

A Novel One‐Pot Conversion of Allyl Alcohols into Primary Allyl Halides Mediated by Acetyl Halide

AbstractA new and simple method for the synthesis of the primary allyl chlorides and bromides 9–16 from the secondary or tertiary allyl alcohols 3–8 and acyl halide was developed (Scheme 2, Table 1). Non‐commercially available secondary and tertiary allyl alcohols were synthesized from the related ketones and aldehydes via the addition of vinylmagnesium chloride. Mechanistic studies indicate that the alcohols were first acetylated by the acetyl halide and then protonated prior to substitution by the halide, Cl− or Br−, via an SN2′ reaction, to yield the primary halides (Scheme 5).

Formation of Surface-Bound Acyl Groups by Reaction of Acyl Halides on Ge(100)−2×1

We have investigated the reaction of a series of acyl halides, including acetyl chloride, acetyl bromide, acetyl-d3 chloride, benzoyl chloride, and pivaloyl chloride, on Ge(100)-2x1 with multiple internal reflection infrared (MIR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). Infrared spectra following saturation exposures of acetyl chloride and acetyl bromide to Ge(100)-2x1 at 310 K are nearly identical, both exhibiting strong nu(C=O) stretching peaks near 1685 cm-1 and no vibrational modes in the nu(Ge-H) region. These data provide strong evidence for the presence of a surface-bound acetyl group on Ge(100)-2x1, which results from a C-X dissociation reaction (where X=Cl, Br). For acetyl chloride, DFT calculations predict that the barrier to C-Cl dissociation is only 1 kcal/mol above a chlorine-bound precursor state and is considerably smaller than barriers leading to the [2+2] C=O cycloaddition and alpha-CH dissociation products. In addition to the C-X dissociation product, both infrared and photoelectron results point to the presence of a second structure for acetyl halides where the oxygen of the surface-bound acetyl group donates charge to a nearby surface atom. This interaction is not observed for benzoyl chloride and pivaloyl chloride.

Synthesis of arbutin by two-step reaction from glucose

Arbutin was synthesized from glucose by two-step reaction below: (a) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl chloride or bromide was prepared by glucose and acetyl halide (chloride or bromide). (b) 2,3,4,6-tetra-O-acetyl-alpha-D-glucosyl halide (Cl, Br) reacted with hydroquinone, methanol as solvent at pH=9.5-10.0.

Equilibrium Between Acetaldehyde, Acetyl Halide and Corresponding 1-Haloethyl Acetates in Gas Chromatograph Injector. Calculation of Enthalpies of Reaction

Gas chromatographic analysis of 1-chloroethyl acetate and 1-bromoethyl acetate revealed that the equilibrium between acetaldehyde, acetyl halide and the corresponding 1-haloethyl acetates exists in the injector of the chromatograph. Analyses were performed under strictly isothermal conditions of both injector and column at different temperatures. The results allowed calculation of the enthalpy of the reaction: CH3CHO + CH3COX → CH3COOCHXCH3 Enthalpies calculated for the reaction are as follows: −17.3 [kcal mol−1] (X=Cl) and −18.5 [kcal mol−1] (X=Br).

Reaction of 2,4-Dibromoquinoline with Hydrogen Chloride

It is known that nucleophilic aromatic substitution in nitrogen-containing heterocycles by the action of such weak nucleophiles as halide ions is very difficult to occur, even when the heteroring is activated by N-oxide moiety. For example, replacement of nitro group in heteroaromatic N-oxides requires severe conditions: heating with concentrated hydrohalic acids at the boiling boint or using acetyl or phosphinoyl halides [1]. According to the recent data, SN reactions of 4-nitroquinoline N-oxide in aprotic solvents are favored by formation of molecular complexes with p(tetracyanoethylene) [2] and especially v-acceptors (H, BF3, AlCl3) [3]. As a result, the corresponding products are formed in quantitative yield under mild conditions.

Convenient Synthesis of Aryl‐Substituted Halo Olefins from Aromatic Ketones and Acetyl Halides in the Presence of Silica Gel Supported Zinc Halides.

AbstractFor Abstract see ChemInform Abstract in Full Text.