Evidence for molecular complexes in the mechanism of additions of iodine mono-chloride to alkenes

1984 ◽  
Vol 62 (11) ◽  
pp. 2526-2534 ◽  
Author(s):  
George H. Sçhmid ◽  
James W. Gordon
Keyword(s):  
Absorption Band ◽  
Equilibrium Constant ◽  
Molecular Complex ◽  
Molecular Complexes ◽  
Electrophilic Addition ◽  
Reaction Coordinate ◽  
Rate Law ◽  
Rate Determining Step ◽  
Enthalpy Changes ◽  
Enthalpy Of Activation

Immediately upon mixing ICls and 2,3-dimethyl-2-butene in CCl4 at 25 °C a new absorption band due to an alkene–ICl molecular complex appears at 295 ± 5 nm and decreases rapidly with time. The rate law under conditions of (alkene)0 [Formula: see text] (ICl)0 for the electrophilic addition of ICl to 2,3-dimethyl-2-butene, E- and Z-2-butene, and E- and Z-1-phenylpropene is −d(ICl)/dt = kexpt(alkene)(ICl)3/{1 + kAD(alkene)}3 where KAD is the equilibrium constant for the formation of a 1:1 alkene–ICl molecular complex. The addition of ICl to the Z and E isomers of 2-butene and 1-phenylpropene occurs by anti-stereospecific addition. The negative enthalpy of activation for the addition of ICl to 2,3-dimethyl-2-butene is evidence that one or more complexes are involved on the reaction coordinate prior to the rate-determining step. On the basis of analysis of the enthalpy changes during the reaction, it is proposed that both a 1:1 and a 1:2 alkene–ICl molecular complex is involved in the mechanism prior to the rate-determining step.

Conductometric Studies of Molecular Complexes of Charge Transfer Type Formed between Aza-Aromatics and Haloanils

1993 ◽  
Vol 58 (4) ◽  
pp. 783-790 ◽  
Author(s):  
Harbhajan S. Randhawa ◽  
Rajni Lakhani
Keyword(s):  
Electrical Conductivity ◽  
Charge Transfer ◽  
Ionization Potential ◽  
Equilibrium Constant ◽  
Molecular Complex ◽  
Molecular Interaction ◽  
Lone Pair ◽  
Molecular Complexes ◽  
Nitrogen Ring ◽  
Ct Complexes

Electrical conductivity technique has been employed to investigate the molecular interaction of aza-aromatics viz. pyridine, α-pikoline, β-picoline and γ-picoline with haloanils, namely chloranil, bromanil and fluranil. The stoichiometry of the charge transfer (CT) complexes has been established and molar conductivities of the complexes determined employing the method of Gutmann and Keyzer. A model has been proposed for determining the equilibrium constant (K) of 1 : 1 molecular complexes of CT type by conductometric measurements. The model involves the assumption: 1/σ = [(1 + K c0A)/qdK c0A] (1/c0D) + (1/qd c0A), where σ is the conductivity of the molecular complex, qd is the extent of depolarization of the complex, c0A) and c0D) are the initial concentrations of the acceptors and donors, respectively. The values of K and qd follows the expected trend of the conductometric parameters determined by the method of Gutmann and Keyzer as well as ionization potential of donors, thereby substantiating the validity of the model proposed. The observed and theoretical values of thermodynamic parameters for the aza-aromatic-chloranil systems that the interaction of aza-aromatics with haloanils is occurring through the lone pair of nitrogen ring.

Influence of alkene structure on the formation constants of alkene–ICl molecular complexes

1986 ◽  
Vol 64 (11) ◽  
pp. 2171-2174 ◽  
Author(s):  
George H. Schmid ◽  
James W. Gordon
Keyword(s):  
Molecular Complex ◽  
Formation Constant ◽  
Addition Reaction ◽  
Molecular Complexes ◽  
Formation Constants ◽  
Experimental Conditions ◽  
Rate Law ◽  
Effect Of Substituents

The experimentally determined rate law for the addition of ICl to 22 alkenes in CCl4 at 25 °C under conditions of (alkene)0 [Formula: see text] (ICl)0 is −d(ICl)/dt = kexp(alkene)0(ICl)3/{1 + C2(alkene)0}3. The constant C2 is shown to be equal to Kapp which is a measure of the formation constant or constants of the molecular complexes in this system. Under the experimental conditions used, C2 is a good approximation of the formation constant of the 1:1 alkene–ICl molecular complex. Thus the values of C2 obtained allow an estimate of the effect of alkene structure on the formation constant of the first molecular complex involved in this addition reaction. The contribution of the effect of substituents on C2 is estimated to be approximately 24% of the overall change in rate due to change in the alkene structure.

scholarly journals Polymer Optical Waveguide Sensor Based on Fe-Amino-Triazole Complex Molecular Switches

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 195
Author(s):  
Muhammad Shaukat Khan ◽  
Hunain Farooq ◽  
Christopher Wittmund ◽  
Stephen Klimke ◽  
Roland Lachmayer ◽  
...  
Keyword(s):  
Molecular Complex ◽  
Electromagnetic Interference ◽  
Optical Power ◽  
Uv Curing ◽  
Molecular Complexes ◽  
Core Material ◽  
Absorption Bands ◽  
Electronic Temperature ◽  
Polymer Waveguide ◽  
Temperature Detection

We report on a polymer-waveguide-based temperature sensing system relying on switchable molecular complexes. The polymer waveguide cladding is fabricated using a maskless lithographic optical system and replicated onto polymer material (i.e., PMMA) using a hot embossing device. An iron-amino-triazole molecular complex material (i.e., [Fe(Htrz)2.85(NH2-trz)0.15](ClO4)2) is used to sense changes in ambient temperature. For this purpose, the core of the waveguide is filled with a mixture of core material (NOA68), and the molecular complex using doctor blading and UV curing is applied for solidification. The absorption spectrum of the molecular complex in the UV/VIS light range features two prominent absorption bands in the low-spin state. As temperature approaches room temperature, a spin-crossover transition occurs, and the molecular complex changes its color (i.e. spectral properties) from violet-pink to white. The measurement of the optical power transmitted through the waveguide as a function of temperature exhibits a memory effect with a hysteresis width of approx. 12 °C and sensitivity of 0.08 mW/°C. This enables optical rather than electronic temperature detection in environments where electromagnetic interference might influence the measurements.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

scholarly journals Influence of the number of water molecules on the mechanism of N-sulfinylaniline hydrolysis

2005 ◽  
Vol 83 (9) ◽  
pp. 1588-1596 ◽  
Author(s):  
Elena V Ivanova ◽  
Heidi M Muchall
Keyword(s):  
Water Molecule ◽  
Density Functional ◽  
Weak Interactions ◽  
Activation Barrier ◽  
Water Molecules ◽  
Functional Theory ◽  
High Enthalpy ◽  
Rate Determining Step ◽  
Enthalpy Of Activation ◽  
Hydrolysis Of

The mechanism of the uncatalyzed hydrolysis of N-sulfinylaniline (Ph-N=S=O) has been studied with B3LYP/6-31+G(2d,2p) in the gas phase, with explicit treatment of water molecules. Hydrolysis involves water attack on sulfur, with a close to perpendicular alignment of a water molecule and the NSO plane in both prereaction complexes and transition states for the rate-determining step. Consequently, the distance of the weak S···O interaction, together with the efficiency of protonation of either nitrogen (attack across the N=S bond) or oxygen (attack across the S=O bond) atoms of the NSO group, determines the height of the activation barrier for hydrolysis. While the reaction with one water molecule is characterized by an unreasonably high enthalpy of activation, a cooperative effect from the weak interactions appears with the inclusion of a second water molecule, where both participate in the reaction, and the activation enthalpy drops significantly. The preference for attack across the S=O bond that is found in the reaction with one water molecule switches to a dominance of attack across the N=S bond in the reaction with three water molecules.Key words: N-sulfinylaniline, hydrolysis, mechanism, density functional theory (DFT).

Adsorption of herbicide-derived anilines in dilute aqueous montmorillonite suspensions

Clay Minerals ◽  
1979 ◽  
Vol 14 (1) ◽  
pp. 1-11 ◽  
Author(s):  
A. Moreale ◽  
R. Van Bladel
Keyword(s):  
Temperature Coefficient ◽  
Equilibrium Constant ◽  
Divalent Cations ◽  
Exchangeable Cation ◽  
Exchange Cation ◽  
Adsorption Mechanisms ◽  
Enthalpy Changes ◽  
Oxidizing Power ◽  
Main Factors ◽  
Good Agreement

AbstractAdsorption isotherms of aniline and p-chloroaniline were determined from very dilute solutions on montmorillonite saturated with different cations (i.e. Na+, K+, Ca2+, Mg2+, Cu2+, Fe3+ and Al3+).In all cases p-chloroaniline was absorbed to a greater extent than aniline. The shapes of the isotherms depend on the adsorbate and on the exchangeable cation and are interpreted in terms of adsorption mechanisms.For aniline, the solvation of the adsorbate and the electronegativity of the saturating cation seem to be the main factors, whereas for p-chloroaniline the polarizing power of the exchange cation plays an important part. In the case of the Fe3+ ion the oxidizing power seems also be involved.The enthalpy changes (ΔH°), calculated from the temperature coefficient of the equilibrium constant are exothermic but less exothermic as the polarizing power of the exchange cation increases. The adsorption of the amines on Na-, K- and Ca-, Mg-montmorillonite gives rise to an entropy loss which is higher for the divalent cations. This result is in good agreement with desorption curves obtained after several washings which indicated for the nature of the organo-clay complexes the decreasing order of stability, viz Mg2+ > Ca2+ > K+ > Na+.

Unusual molecular complexes of antimony fluoride dimers with Acetonitrile and Pyridine: structures and bonding

2021 ◽  
Author(s):  
Elena I. Davydova ◽  
Alexander Viktorovich Virovets ◽  
Eugenia V. Presypkina ◽  
Anna Vladimirovna Pomogaeva ◽  
Anna S Lisovenko ◽  
...  
Keyword(s):  
Molecular Complex ◽  
Molecular Complexes ◽  
Antimony Pentafluoride ◽  
Antimony Trifluoride

Structures of two new molecular complexes of antimony pentafluoride with pyridine (Py) and acetonitrile (AN), SbF5•Py and Sb2F10•AN, as well as a molecular complex of antimony trifluoride Sb2F6•Py and its...

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