Reaction Of Alkyl Halides Research Articles

Bimolecular reactions of alkyl halides and acylgermanes: formation of ketones, diketones, and other products by radical-radical reaction

Reactions of alkyl halides (R 1X) with acyltriphenylgermanes (R 2COGePh 3) under radical conditions provide mixtures of ketones (R 1COR 2), diketones (R 2COCOR 2), alkanes (R 1H) and alkenes. These products arise from radical-radical reactions, and the results suggest that bimolecular addition reactions of alkyl radicals to acylgermanes are too slow to propagate radical chains.

Carbon-13 Chemical Shift Tensors for Acylium Ions: A Combined Solid State NMR and Ab Initio Molecular Orbital Study

We report the principal components of the 13C chemical shift tensors for seven acylium ions, determined by both slow speed magic angle spinning (MAS) nuclear magnetic resonance (NMR) and theoretical methods. Experimentally, the acylium ions were prepared either by direct reaction of the parent acyl halides with metal halide powders, including frozen antimony pentafluoride, or by the reaction of alkyl halides with carbon monoxide on aluminum chloride (AlCl3). The generalization of our recent observation of the acetylium ion on AlCl3 to other cations is direct proof of free acylium ion intermediates in Friedel−Crafts acylation reactions. 13C CP MAS NMR spectra of the acylium ions were acquired at temperatures ranging from 83 to 298 K, and the principal components of the 13C chemical shift tensors were extracted by fitting the side band intensities of the MAS spectra. With the exception of the chloroacetylium ion, the acylium ions studied have isotropic 13C1 chemical shifts of 154 ± 1 ppm, but clear variations in the principal components of the shift tensors were measured. The carbenium carbons of the acetylium and 2,2-dimethylpropionylium ions have axially symmetric 13C chemical shift tensors, consistent with the molecular symmetry (C3v), while the chemical shift tensors of the other cations were characterized by non-zero asymmetry parameters. The observation of appreciably smaller chemical shift anisotropies for C1 in the benzoylium ions versus the values for the corresponding carbon in the alkanoyl cations is consistent with charge delocalization into the ring substituent. Additional information on the acylium cations is provided by theoretical calculations. We optimized the geometries of the acylium ions using second-order Møller-Plesset perturbation theory (MP2) and the 6-311G* basis set. We then calculated the NMR data at the MP2 level using the gauge-including atomic orbital (GIAO) method and the double-ζ (dz) and triple-ζ polarized (tzp) basis sets of Horn and Ahlrichs. While the isotropic shifts calculated at the GIAO-RHF/tzp/dz level were in error by as much as 26 ppm, the GIAO-MP2 values were in excellent agreement with the experimental measurements, as were those for most of the principal components. The calculations were also used to determine the orientations of the principal components. The results of analysis of the MP2 wave functions help answer long standing questions regarding the structure and bonding of acylium cations.

Applications of temperature scanning in kinetic investigations: The hydrolysis of acetic anhydride

The temperature scanning methods described here are widely applicable. They can be used in kinetic investigations on many other liquid-phase reactions with similar chemical kinetics: for example, the hydrolysis reactions of alkyl halides and esters, including both acid- and base-catalyzed reactions. In more complicated cases the temperature scanning methods require more sophisticated data handling procedures but they continue to yield the correct overall (net) rates of reaction. We leave such cases for future consideration and confine ourselves to this simple system where diffusion and heat transfer rates are clearly unimportant.

Synthesis and asymmetric alkylation of glucose-derived bicyclic oxazinones: An evaluation of their use as “chiral glycines”

We have prepared structurally novel bicyclic oxazinones based on D-glucopyranose. The lithium enolates of these compounds undergo highly diastereoselective alkylation reactions with reactive alkyl halides, in modest yields. Use of the phosphazene P4 base enhances the yields of these processes, suggesting that metal enolate aggregation is at least partly responsible for the depressed yields. The stereochemistry of the products has been unequivocally ascertained by nOe measurements and ab initio calculations.

Cross-linking of hydropolysilanes for use as silicon carbide precursors

Cross-linking reactions of hydropolysilanes with alkyl halides as cross-linking agents were evaluated in order to obtain high yields of oxygen-free silicon carbide ceramics. On the basis of data from infrared spectroscopy, thermogravimetry, solubility, gel permeation chromatography, and ultraviolet spectroscopy, it has been found that the cross-linking reactions of the polymer occurred to varied extents depending on the type of alkyl halides used. The reactivities of alkyl halides to hydropolysilanes were found to be dependent on the type of halogen, the number of halogen atoms attached to the same carbon atom, the size of the alkyl group, and the reaction temperature.

The reaction mechanism of alkyl halides with carbon dioxide catalyzed by 5,10,15,20,-tetraphenyl porphyrin cobalt (CoTPP)

Benzyl chloride and butyl halide each react with CO 2 catalyzed by 5,10,15,20-tetraphenylporphyrin cobalt (CoTPP) to form phenylacetic acid (in the form of benzyl phenylacetate, the product of electrocarboxylation) or oxalic acid (the direct reduction product of CO 2, in the form of dibutyl oxalate), respectively. The data show that electrocarboxylation of benzyl chloride reacting with CO 2 can occur, but butyl halide in the presence of CO 2 cannot produce the electrocarboxylation product amylic acid. The reasons for the different mechanisms are examined through the reaction of alkyl halide with CoTPP studied by electrochemistry and spectroelectrochemistry. The intermediate N-alkyl CoTPP is detected by spectroelectrochemistry in situ. The reasons that they form different products with different N-alkyl CoTPP are discussed in detail.

Synthesis and Characterization of Chiral Nitronic Esters via O-Alkylation of (4S*,5R)-(+)-4-(1‘-Nitro-1‘-carbethoxymethyl)- 5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone with Alkyl Halides

A series of stable and enantiomerically pure alkyl nitronic esters are synthesized in good to excellent yields via O-alkylation of (4S*,5R)-(+)-4-(1‘-nitro-1‘-carbethoxymethyl)-5-[(1R)-menthyloxy]-3,4-dihydro-2(5H)-furanone (4a) with alkyl halides in the presence of K2CO3 and DMF at room temperature. Thus, nitronic esters are obtained for the first time from the alkali metal salt of a nitro compound and various alkyl halides, which refutes the traditionally held view that the reaction of alkyl halides with alkali metal derivatives of nitro compounds gives a carbonyl compound and an oxime, rather than a nitronic ester. Secondary alkyl nitronic esters are found to partially decompose into O-alkyloximes. The configurations of the nitronic esters and O-alkyloximes were assigned to be Z on the basis of the NOE experiments. The synthesis of the nitro furanone 4a and its enolization to form a six-membered intramolecular hydrogen bond structure are described.

A Facile Method for the Syntheses of Dialkyl Disulfides from Sulfur Under Phase Transfer Conditions

Abstract A convenient reaction of alkyl halides with sulfur in alkaline medium has been found to afford disulfides in good to excellent isolated yield under phase transfer conditions.

Chart for Deciding Mechanism for Reaction of Alkyl Halide with Nucleophile/Base

The decision chart offered here is based upon the well-known and accepted characteristics of the reaction system mechanisms described in typical introductory organic chemistry textbooks.

Amides as nucleophiles: reaction of alkyl halides with amides or with amides and water. A new look at an old reaction. [Erratum to document cited in CA118:191099

Amides as nucleophiles: reaction of alkyl halides with amides or with amides and water. A new look at an old reaction. [Erratum to document cited in CA118:191099

Reduction with 2-Propanol over Hydrous Tin(IV) Oxide

Abstract The reduction with 2-propanol as a hydrogen source over hydrous tin(IV) oxide has proved to be successful. Hydrous tin(IV) oxide was prepared from stannic(IV) chloride by precipitation with aqueous ammonia, followed by drying and calcination at 300 °C for 5 h. The specific surface area was 150 m2 g−1. The reductions were carried out in the vapor phase at temperatures of from 300 to 330 °C. The reduction of aliphatic carboxylic acids gives the corresponding alcohols. Aromatic carboxylic acids and their derivatives were further reduced, and the corresponding hydrocarbons were obtained. The reductions of aromatic ketones and the derivatives of benzyl alcohol also gave hydrocarbons. In the reaction of alkyl halides, reductive dehalogenation proceeded and the corresponding hydrocarbon was produced.

Bifunctional chiral auxiliaries 6: Alkylations of enolates derived from 1,3-diacylimidazolidine- 2-thiones and 1,3-diacylimidazolidin-2-ones

Sodium and potassium enolates of 1,3-diacylimidazolidin-2-ones undergo clean alkylation reactions with reactive alkyl halides; the latter enolates reacting generally more stereoselectively due, it is proposed, to the lower temperature at which the reactions proceed. The reactions are all stereoregular, with the diastereoisomeric identity of products being established unambiguously by the synthesis of (2 S)-3-phenyl-2-methylpropan-1-ol. The sense of asymmetric induction in these reactions is consistent with the intermediacy of chelated syn enolates which the electrophile approaches preferentially from the face exo to the proximate alkyl / aryl group on the five-membered ring. In contrast, 1,3-diacylimidazolidine-2-thiones are unable to act as bifunctional chiral auxiliaries in alkylation reactions due to enolate decomposition.

The Chemistry of 5-Oxodihydroisoxazoles. X. Butyllithium and Lithium Diisopropylamide Promoted Rearrangements of 3-Unsubstituted Isoxazol-5(2H)-ones

The reaction pathway of 3-unsubstituted isoxazol-5(2H)-ones with bases, proposed by Woodman1-3 to proceed via four intermediates to azetidine-2,4-diones, has been confirmed by the isolation of products unequivocally derived from each of the intermediates. Isoxazol-5(2H)-ones substituted on nitrogen by methyl, phenyl, quinolin-2-yl and vinyl groups have been studied. The azetidine-2,4-diones have only been isolated when the intermediate enolate has been alkylated , but only reactive alkyl halides lead to useful syntheses.

Free‐Radical Coupling of Alkyl and Aryl Halides with Electron‐Deficient Alkenes Mediated by Chromium(II) Complexes[1]

AbstractFree radicals generated from organic halides and (ethylenediamine)chromium(II) complexes in DMF are trapped by electron‐deficient olefins. The coupling reactions of alkyl halides, described in Part I[1], are extended and, in addition, aryl halides are shown to be efficient radical precursors to yield coupling products in good yield.

ChemInform Abstract: Organosamariums from Reaction of Alkyl Halides with Samarium(II) Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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.

Amides as nucleophiles: reaction of alkyl halides with amides or with amides and water. A new look at an old reaction

Heating of formamide with an alkyl halide (with or without water) affords a mild, nonhydrolytic, high-yield synthesis of alcohols and formate esters. Yet the way in which substitution on the alkyl halide actually occurs remains occure. To explore this question, thermal reaction of 1-bromooctane (1a) with formamides (HC(O)NHR, R=H, Me; 2a, 2b) was studied quantitatively. Major products are 1-octanol (3) and n-octyl formate (5); minor products are 1-octene (4), di-n-octyl ether (6), and N-octylformamide (7, from 2a, only)

Novel precursors for chemically assisted ion beam etching : reactions of dichloroethane on GaAs (100)

The potential advantages of chemically assisted ion beam etching (CAIBE) over reactive ion beam etching (RIBE) are considered for GaAs. The ideal form of etching precursor that CAIBE requires is discussed, with particular reference to use of the technique for in situ etching in an ultra-high vacuum environment. To investigate various candidates for this role requires a detailed insight into the microscopic surface reactivity of the molecular species concerned on GaAs and the effect of an impinging inert gas ion beam. A systematic study into the reactivity of alkyl halides on GaAs (100) has been undertaken through the use of in situ surface spectroscopic probes and this paper reports the first insight into the adsorption and beam induced behaviour of 1,2 dichloroethane. Dissociative chemisorption is seen to occur initially giving a bound Cl layer and by-products which can be desorbed without leaving surface carbon. Higher exposures give rise to molecular physisorption. This form of behaviour is ideal for CAIBE purposes. However, argon beam bombardment can lead to some fragmentation of the molecular species. This effect is discussed in terms of the contamination that may arise during GaAs etching.

A reinvestigation of the reaction of [Fe 2(η-C 5H 5) 2(CO) 4- n(CNR) n] ( n = 1 or 2) with strong alkylating agents

The reaction of [Fe 2(η-C 5H 5) 2(CO) 3(CNR)] with R′OSO 2CF 3 (R,R′  Me or Et) gives a mixture of cis and trans-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CO)μ-CN(R′)R]SO 3CF 3. When R  R′  Me the isomer ratio is variable, but the cis always predominates and is the only product when R ≠ R′. The complexes [Fe 2(η-C 5H 5) 2(CO) 2(CNR) 2] react with R′OSO 2CF 3 and the more reactive alkyl halides R′X to give a mixture of cis- [Fe 2(η-C 5H 5) 2(CO)(CNR)(μ-CO)ν-CN(R′)R]X and cis-[Fe 2(η-C 5 H 5) 2(CO) 2μ-CN(R′)R 2][X] 2. In both series of cations the presence of μ-CN(R′)R ligands give rise to isomers that differ in respect of orientation about the CN bond. The cations are not fluxional and do not undergo cis- trans interconversion, bridge-terminal ligand exchange, or rotation about the μ-CN(R′)R double bond. The structure of the cations in the [Fe 2(η-C 5H 5) 2(CO)(CNMe)(μ-CO)(μ-CNMe 2)]BPh 4 and [Fe 2(η-C 5H 4Me) 2(CO) 2(μ-CNMe 2) 2][SO 3CF 3] 2 salts were confirmed as cis by X-ray diffraction studies. Their dimensions are similar to those previously found in cis- [Fe 2(η-C 5H 4Me) 2(CO) 2(μ-CO)(μ-CNMe 2)]I, but with variations due to the differing acceptor and donor abilities of the various ligands. Infrared and NMR spectra of the complexes are reported and discussed.

The Role of Ion Beam Assisted Surface Chemistry in Etching: Adsorption and Reactions of ALKYL Halides

ABSTRACTThe form of ideal surface chemistry that is necessary for chemically assisted ion beam etching (CAIBE), with particular reference to in-situ processing is considered. Whilst to date CAIBE has been almost exclusively carried out with chlorine, distinct advantages exist if a compound that which displays spontaneous reactivity which is limited to one or two monolayers can be used. The role of alkyl halides in this scenario has been investigated through the use of surface spectroscopic probes to investigate the microscopic chemical and ion beam assisted reactivity that may be achieved. Dichloroethane has been found to display promising behaviour.

Organosamariums from Reaction of Alkyl Halides with Samarium(II) Derivatives

Bis(cyclopentadienyl)samarium (SmCp2) and alkyl halides gave organosamariums stable at -10 °C and reactive towards electrophiles. Samariuim(II) iodide did not give stable alkylsamariums. However internal quenching with ethan[2H]ol provided high yields of the monodeuterated alkane. In the latter case, an unstable organosamarium species was formed which needed an in situ trapping agent. The samarium analogue of the Barbier reaction is discussed in the light of these results. Some additional Barbier experiments were performed in the presence of samarium(II) iodide in tetrahydrofuran. It is concluded that under standard conditions (in the absence or presence of hexamethylphosphoramide) an unstable and reactive organosamarium species is formed which is immediately trapped by the carbonyl compound.