Tert-butyl Halides Research Articles

Properties of the tert-butyl halide solvolysis transition states.

We have obtained properties (or descriptors) of the transition states in the solvolysis of tert-butyl chloride, bromide and iodide. We show that all three transition states, in both protic and in aprotic solvents, are highly dipolar and are strong hydrogen bond acids and strong hydrogen bond bases, except for the tert-butyl iodide transition state in aprotic solvents, which has a rather low hydrogen bond acidity. Thus, the transition states are stabilized by solvents that are hydrogen bond bases (nucleophiles) and are hydrogen bond acids (electrophiles). We show also that the partition of the transition states between water and solvents is aided by both nucleophilic and electrophilic solvents and conclude that the rate of solvolysis of the three halides is increased by both nucleophilic and electrophilic solvents.

Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis.

Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium‐catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4‐chlorobutan‐2‐one or tert‐butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional‐group tolerance and safety profile of these reactions compared to the state‐of‐the‐art. This method has granted access to alkenyl halide compounds containing acid‐sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram‐scale synthesis where low catalyst loading was achieved.

Unexpected Indirect Dynamics in Base-Induced Elimination.

Base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) are two of the most versatile reactions that are important in preparative organic chemistry. These stereospecific reactions are often found in direct competition with each other. Elimination can proceed via two distinct transition states, referred to as anti and syn, of which anti is commonly energetically favored. To investigate the intrinsic dynamics of base-induced elimination, reactions under single-collision conditions are required. Here, we present reactive scattering results on the prototype reaction of the fluoride anion with tert-butyl halides. The observed mechanistic fingerprints are associated with the E2 reaction, because steric hindrance at the α-carbon suppresses the SN2 reaction [Carrascosa, E.; Meyer, J.; Zhang, J.; Stei, M.; Michaelsen, T.; Hase, W. L.; Yang, L.; Wester, R. Nat. Commun. 2017, 8, 25]. The reaction coordinate shows energetically submerged transition states, with anti favored over syn, and we found a very shallow prereaction well for anti. We predominantly found indirect dynamics for a range of collision energies, which can be separated into three remarkably different mechanisms. At low collision energies, the first is a large impact parameter indirect mechanism which leads to a forward-backward symmetric scattering signature. The second mechanism is attributed to low-impact parameter reactions with a near-statistical partitioning of the total available energy. The majority of events are associated with widespread isotropic scattering. Unexpectedly, the product ion kinetic energy distributions are independent of collision energy. We associate this with dynamic trapping in a prereaction well supported by a large centrifugal potential. These measured fingerprints support that atomistic reaction dynamics cannot be predicted based on stationary arguments alone.

Elucidating the mechanism of cob(I)alamin mediated methylation reactions by alkyl halides: SN2 or radical mechanism?

Methyl transfer reactions mediated by cobalamins (Cbls) have been considered as one of the most important biologically relevant molecular transformations for many enzymatic reactions catalyzed by Cbl-dependent enzymes. The exact mechanism of methyl transfer reactions involving Cbls is still poorly understood. To investigate the mechanistic details of Cbl mediated methylations by alkyl halides, density functional theory (DFT) along with the polarizable continuum model (PCM/water) for solvation has been applied. Two different mechanisms have been examined, namely SN2 and radical-based electron transfer (ET) to elucidate the methyl transfer reaction. The calculations have suggested that the methyl transfer from methyl halides proceeds through SN2 nucleophilic displacement. However, with more bulky alkyl substrate, namely isopropyl and tert-butyl halides the reaction followed the ET-based radical pathway which is associated with an ET from diradical form of cob(I)alamin to alkyl halides. Our proposed mechanism for alkyl transfer reaction corroborates with the experimental findings, which reported a mechanistic switch from a two-electron (SN2-type) to a one-electron mechanism for sterically demanding alkyl halides. The present theoretical contribution provides more in-depth insight into the methyl transfer reaction catalyzed by corrinoid-dependent methyltransferases.

Extent of Nucleophilic Participation in the Solvolyses of Alkyl Chloromethyl Ethers and Sulfides

The specific rates of solvolysis have been determined for chloromethyl ethyl ether (3) and chloromethyl octyl ether (4) at −10.0 °C and for chloromethyl methyl sulfide (5) at 25.0 °C in a variety of pure and binary solvents. These values were used for a correlation analysis treatment using the extended Grunwald–Winstein equation incorporating literature values for solvent nucleophilicity ( NT) and solvent ionising power ( YCl). Appreciable values were found for the sensitivities towards changes in both NT and YCl values. Using a literature specific rate of hydrolysis at 25.0 °C for fluoromethyl methyl ether (2), the required value for chloromethyl methyl ether (1) was obtained from use of NT and YCl values and the sensitivities for 3 to changes in their values, to adjust an experimental specific rate value for 1 in 100% ethanol to the corresponding value in 100% water. In this way, an estimated kCl/ kF of 1.2 × 105 was obtained, essentially identical to values for the solvolyses of tert-butyl halides. A unimolecular mechanism for the solvolyses, with appreciable nucleophilic solvation of the developing carbocation, is proposed. Electronic supplementary information provides, for several solvents, specific rates of solvolysis for 3, 4, and 5 at additional temperatures and the calculated activation parameters.

Liquid-Phase Isobutane/Butene-Alkylation Using Promoted Lewis-Acidic IL-Catalysts

The effect of different promoters on activity and selectivity of Lewis-acidic chloroaluminate ionic liquid catalysts was studied for isobutane/2-butene alkylation. When tert-butyl halides are used as promoters, the active species of the alkylation reaction, which is the tert-butyl cation, is directly generated whereas upon catalysis with Bronsted-acid supported ionic liquids, this species is indirectly provided through a hydride shift between protonated 2-butene and isobutane. Experimental results both from batch and continuously operated liquid phase alkylation reactors indicate, that tert-butyl halides are able to speed up the reaction rate significantly and shift the C8-selectivity towards the desired high-octane trimethylpentanes (TMPs). However, secondary reactions like oligomerization and cracking could not be suppressed by the use of this additives and high deactivation rates in continuous opperation were observed. Suggestions are made, how the product composition is effected by the additive and how the promoted IL-catalyst system is deactivated with time on stream.

Infrared vibrational spectra of tert-butyl halides in low-aluminum H-Y Faujasite: Vibrational excitation exchange and other effects of guest–host interactions

Fourier transform infrared (FTIR) studies at 295 K of low-aluminum H-Y (LAHY, Si/Al = 40) faujasite zeolite supercage-included tert-butyl halides, (CH 3) 3C–X (X = Cl, Br, I), are presented in comparison with the adsorbate molecular gas-phase and unloaded host solid-state spectra. The FTIR results, aided by computer modeling studies, reveal a propensity toward the exchange of quanta of vibrational excitation between guest modes, and between guest and host modes. The exchange phenomenon and some pseudo-hydrogen bonding effects are related to the siting of the guest molecules in the host supercage, and to the guest–host interactions at the guest site.

A DFT study of SN 2 and E 2 reactions of butylhalides on zeolite Y: The effect of the leaving group

A density functional theory (DFT) study of adsorption and reaction of n-butyl, sec-butyl, and tert-butyl halides was carried out at B3LYP/6-311+G(d,p)//B3LYP/6-31+G(d,p) level of calculation, using a NaT 3 (T=Si, Al) cluster to represent the zeolite active site. The results show that the adsorption of the alkyl halides on the zeolite surface involves a charge–dipole interaction and is exothermic with respect to the isolated reactants, especially for butylchlorides. The formation of alkoxy species, through a S N2 type reaction mechanism, is lower in energy than proton elimination, through E2 type reaction mechanism, for the primary and secondary halides. This behavior is more accentuated for butylchlorides than for the other butyl halides. For the reactions with butyl bromides and iodides with NaT 3 cluster, the difference between the energy barriers for alkoxide formation and proton elimination is lower than for the respective chlorides. For the tert-butyl halides, proton elimination was the only reaction found possible in the calculations.

Effects of tert-Butyl Halide Molecular Siting in Crystalline NaX Faujasite on The Infrared Vibrational Spectra

Experimental, analytical, and modeling techniques employed in this study elucidate interactions between adsorbate molecules and the interior surfaces of the porous host faujasite. The vibrational spectroscopies of guest and host offer opportunities to locate the guest site in the host. We present Fourier transform (FT) infrared (IR) studies of sodium-X (NaX) faujasite supercage-included tert-butyl halides, (CH(3))(3)C-X (X=Cl, Br, I) in comparison with the adsorbate molecular gas-phase and host solid-state spectra at 295 K. Four observations of guest (nu(5,) nu(6), nu(7), and {nu(3), nu(16), nu(17)}) vibrational mode changes, three of them concomitant with host mode changes, together with modeling studies, point to a particular preferred siting of the guest molecules at host hexagonal prisms (D6R). The siting involved simultaneous interactions of the host with methyl group axial protons and the halide atom. All three methyl group axial protons interact preferentially with a single D6R O1 oxygen atom via C-H...O bonding. The halide atom also interacts with a site III' Na cation. The cation, in turn, is coordinated by three O atoms (two O1 and an O4). Two of these O atoms (O1) bridge the double six-rings that form the hexagonal prism part of the NaX substructure. O4 connects the two D6R units.

CH Stretching Vibrational Overtone Spectra of tert-Butylbenzene, tert-Butyl Chloride, and tert-Butyl Iodide

The vapor phase CH stretching vibrational overtone spectra of tert-butylbenzene and tert-butyl chloride are measured in the Delta upsilon(CH) = 2-7 region, while the spectrum of tert-butyl iodide is recorded in the Delta upsilon(CH) = 2-6 region. The overtone spectrum of tert-butylbenzene is too complex to make detailed spectral assignments. Local mode frequencies, omega, and anharmonicities, omegax, are obtained for tert-butyl chloride and tert-butyl iodide. The torsional dependencies of the local mode frequency, delta(omega), and anharmonicity, delta(omega)(x), are calculated for the tert-butyl halides. Nonbonded, through-space intramolecular interactions are observed in the blue-shifting of sterically hindered CH oscillators. Scaling factors are presented for relating ab initio calculated local mode parameters to experimental values for alkyl CH oscillators. Fermi resonances are observed between local mode states and local mode/normal mode combination states in tert-butyl chloride and tert-butyl iodide. Vibrational overtone transition intensities are calculated in the range Delta upsilon(CH) = 3-9 using the harmonically coupled anharmonic oscillator (HCAO) model and ab initio dipole moment functions. The resultant HCAO intensities are compared to experimental intensities at Delta upsilon(CH) = 3.

Iron-Containing Graphite as a Friedel-Crafts Alkylation Catalyst

The activity of iron-containing graphites for the Friedel-Crafts reaction of phenol with tert-butyl halides was studied. Graphites were characterized by XRD and XPS. The reaction of phenol with either various tert-butyl halides or tert-butyl alcohol on iron-containing graphite was performed in a benzene solvent for 4 h at 50°C. The conversion and yield of the reaction on iron-containing graphite decreased in the order, tert-butyl iodide, tert-butyl bromide, and tert-butyl chloride, whereas for AlCl3, tert-butyl chloride was the most reactive while tert-butyl iodide was the least. Activated charcoal was not reactive. The presence of iron accelerated the reaction of phenol with the tert-butyl halide on graphite to yield p-tert-butylphenol as the main product. The presence of both tert-butyl bromide and iron increased the distance between the layers of graphite but not in the presence of either the iron or tert-butyl bromide. tert-Butyl halide was first adsorbed on graphite and then dissociated to form tert-butyl and halogen ions. The peak was observed at d=11.9 Å in the XRD pattern of the graphite after the reaction in which the high purity graphite was treated with tert-butyl halide and iron in phenol. This is probably due to the mixture of phenol with tert-butyl ion and iron inserted into the layers of graphite to form a two-stage structure.

Solvolytic Reactions in Fluorinated Alcohols. Role of Nucleophilic and Other Solvation Effects

Rate constants and products for solvolyses of chlorodiphenylmethane (Ph2CHCl) and p-methoxybenzyl chloride in 2,2,2-trifluoroethanol (TFE)/water and TFE/ethanol are reported, along with additional kinetic data for solvolyses of tert-butyl and other alkyl halides (RX) in 97% w/w TFE/water and in 97% w/w hexafluoropropan-2-ol/water (HFIP). Results are discussed in terms of the solvent ionizing power (Y) and the solvent nucleophilicity (N), and contributions from other solvation effects are considered. Comparisons with other SN1 solvolyses show that solvolyses of Ph2CHCl in TFE mixtures are unexpectedly fast, but product ratios are unexceptional. An additional solvation effect influences solvolyses leading to delocalized cations, and a delocalized cationic transition state for concerted elimination may explain the recent results of Takeuchi et al., (J. Org. Chem. 1997, 62, 4904) without the need to postulate additional specific solvation effects for adamantyl systems, such as Bronsted-base solvation of α- and β-hydrogen atoms; concerted elimination may occur because simple tertiary alkyl cations are too unstable to form in predominantly aqueous media. Iodide/bromide and bromide/chloride rate ratios are very similar for 1-adamantyl halides and corresponding solvolyses of tert-butyl halides; these ratios decrease in the order aq EtOH > TFE > HFIP, as expected for an electrophilic solvation effect (this effect can readily be incorporated into Y values). From kinetic data for a series of tertiary alkyl chlorides in 97% TFE/water, it is shown that the susceptibility of rates of solvolyses of RCl to N decreases with an increase in steric hindrance or with an increase in charge stabilization. Also, the small kinetic solvent isotope effects for typical solvolyses (e.g., methyl tosylate) indicate that nucleophilic attack lags behind heterolysis of the C−X bond.

A theoretical analysis of the kinetics of reductive cleavage of the carbon—halogen bond in tert-butyl halides in polar solvent

Rate constants and activation energies of dissociative electron transfer reactions of t-butyl halides proceeding in polar solvent are calculated. A model is used in which potential energy of the bond C-X to be broken is described by a Morse function in reactant and an exponential curve in product. The parameters of the exponential function are taken from quantum chemical calculations of the radical anions of t-butyl halides. The reorganization energy of reaction is computed in the framework of the cavity model. Results of calculations are compared with experimental data.

A study of the carbon-halogen bond breaking in tert-butyl halides by the PM3 quantum chemical method

Quantum chemical calculations by the semiempirical PM3 method are performed for halogen tert-butanes t -BuX (X = Cl, Br) and their radical anions in the gas phase and model polar solvent. It is shown that these radical anions are unstable in polar solvents. Potential energy surfaces for t -BuBr −. and t -BuI −. have shallow minima in the gas phase. In the range of the values of the distances R (C-halogen) from the equilibrium one R 0 to R ≈ 2.2–2.3 A ̊ the potential curves for t -BuCl −. and t -BuBr −. may be well approximated by the exponential functions U f = B exp [−2 β ( R − R 0 )]. Activation energies and the values R ∗ for the transitional configuration for the reactions t -BuX + e → t -Bu . + X − in the gas phase are calculated.

A theoretical model for SN1 ionic dissociations in solution. 3. Analysis of tert-butyl halides

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA theoretical model for SN1 ionic dissociations in solution. 3. Analysis of tert-butyl halidesJeffery R. Mathis, Hyung J. Kim, and James T. HynesCite this: J. Am. Chem. Soc. 1993, 115, 18, 8248–8262Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://doi.org/10.1021/ja00071a038RIGHTS & PERMISSIONSArticle Views377Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Calorimetric study of the solution process of tetramethylsilane in alcohols

Calorimetrically measured enthalpies of solution of tetramethylsilane into 16 alcohols, containing from 1 to 6 carbon atoms, are reported at 25°C and infinite dilution. These values are combined with the vaporization enthalpy of the solute to obtain standard enthalpies of gaseous tetramethylsilane and data are analysed in terms of the solvent structures. The solution functions for tetramethylsilane (TMS) are compared with the solution functions for tert-butyl halides ( t-BuX) in order to obtain information on ert-butyl halide-alcohol interactions. For this purpose, values of solution enthalpies are also determined for tert-butyl chloride, bromide and iodide in pentan-3-ol, 2-methylbutan-2-ol and hexan-1-ol. The limitations of the use of TMS as “inert” model solute of t-BuX are discussed. However, the application of the Onsager reaction field theory is found to be useful in the analysis of the influence of the eccentricity factor on the interaction enthalpy and leads us to conclusions regarding the relative importance of dipolar solute-solvent interaction and solvent reorganization on the solution process of t-BuX in alcohols.

Matrix isolation study of complexation and exchange reactions of molecular halogens with tert-butyl halides

Matrix isolation study of complexation and exchange reactions of molecular halogens with tert-butyl halides

Quantitative formulation of reactivity in terms of solvent and substrate properties. Solvolysis of tert-butyl halides in hydroxylic solvents

Experimental rate constant values for the solvolysis of tert-butyl chloride in 12 alcohols at 25 °C are presented. These results, together with previous data, are well correlated through the linear solvation energy relationship log k=a0+a1 g(η)+a2ENT+a3C where g(η) is a function of the refractive index, ENT is the normalized Dimroth and Reichardt parameter and C is the solvent cohesive energy density. The same is true for tert-butyl bromide and iodide.A statistical treatment relating the experimental values of the solvolytic rate constants of the three halides in the same set of hydroxylic solvents (water, 8 monoalcohols and 10 dialcohols) to the properties of the solvents [g(η), ENT and C] and of the substrate [molar volume (V) and dipole moment (µ)] simultaneously was performed.

Electronic structure of tert-butyl halides and group 14 derivatives: Electron affinities and dissociative electron attachment

Electron transmission (ET) and dissociative attachment (DA) spectroscopies are applied to the tert-butyl halides and to derivatives where the central carbon atom is replaced by a heavier group 14 element. In the tert-butyl halide series, the electron affinity increases with increasing size of the halogen atom, while in the group 14 analogues the electron affinity reaches a minimum value for the silicon derivatives. Bound-state and continuum multiple scattering Xα (MS-Xα) calculations reproduce very closely the energies of the resonances observed in the ET spectra. The DA spectra show that the ground anion state of the tert-butyl halides (except for the fluorine derivative) can decay following a dissociative channel, with halogen anion production. In the group 14 derivatives this mechanism is much less active. In some of the compounds investigated, dissociative capture of thermal electrons is also observed.

Carbonylation of Tertiary Alkyl Halides Synthesis of Pivaloyl Halides

The carbonylation of tert-butyl halides in a two-phase system, RSO 3H/CCl 4, under carbon monoxide pressure affords the corresponding pivaloyl halides in good yields and selectivities.