Remote inductive effects on secondary and tertiary 2-norbornyl solvolysis rates

A 5-cyano substituent decelerates the solvolysis rate of exo-2-norbornyl brosylate $\text{(1-H)}$ by a factor of 1790. A much smaller deceleration (24–90 fold) is observed for the secondary $\text{endo}$ and for both $\text{exo}$ and $\text{endo}$ tertiary 2-norbornyl derivatives. These results support the occurrence of σ-participation in the solvolysis of $\text{1-H}$.     

Solvolysis of 2-aryl-exo-5,6-trimethylene-2-norbornyl p-nitrobenzoates as a reference of 2-aryl-2-norbornyl p-nitrobenzoates solvolysis: Further evidence for the unimportance of σ-participation in the solvolysis of 2-aryl-2-norbornyl derivatives

The rates of solvolysis of 2 - aryl - exo - 5,6 - trimethylene - exo - and endo - 2 - norbornyl p-nitrobenzoates (7 and 8, respectively) with representative substituents [p-CH₃O, p-CH₃, H, m-CF₃, p-CF₃, and 3,5-(CF₃)₂] were determined in 80% aqueous acetone and compared with those of the parent 2-aryl-exo- and endo-2-norbornyl p-nitrobenzoates (5 and 6, respectively). The rate ratios for the endo-p-nitrobenzoates ($\text{6}\text{8}$) are essentially constant and close to unity for these substituents, indicating that the perturbation of the trimethylene bridge toward the C₂-position is virtually negligilbe. The rate ratios for the exo-p-nitrobenzoates ($\text{5}\text{7}$) can also be regarded as invariant over the reactivity range studied. The exo/endo rate ratios ($\text{7}\text{8}$) are 246 (p-CH₃O), 196 (P-CH₃), 129 (H), 80 (m-CF₃), 90 (p-CF₃), and 89 [3,5-(CF₃)₂], being similar to the corresponding $\text{5}\text{6}$ rate ratios. The solvolyses of these p-nitrobenzoates (7 and 8) afford predominantly ( > 97%) exo-alcohols. Since the secondary exo-5,6-trimethylene-2-norbornyl system, with its low exo/endo rate ratio, 11.2, is known to solvolyse without significant σ-participation, the tertiary derivatives should also undergo solvolysis without σ-participation. Consequently, the similarities in the solvolytic behaviors between the two systems (5 vs 7; 6 vs 8) strongly support the previous conclusion that σ-participation is unimportant in the solvolysis of 5.     

Polar effects in the solvolysis of 6-exo-substituted endo-2-norbornyl p-toluenesulfonates

The solvolysis rates of endo-2-norbornyl p-toluenesulfonates $\text{1}$ are affected far less by 6-exo-substituents than are the rates of the corresponding exo-2-norbornyl p-toluenesulfonates $\text{2}$¹.     

Solvolysis of 2-m-chlorobenzoyloxy-4-isopropyl-2h-1,4-thiazin-3-one generation of a stable carbocation

The title compound $\text{2b}$ undergoes nucleophilic substition reactions with exclusive aklyl-oxygen bond fission and its rate of solvolysis is highly sensitive toward change in polarity of solvents, as is shown by its highest m-value of all reported so far in logK - logk₀ = mY.     

The effect of ultrasound on the solvolysis of 2-chloro-2-methylpropane in aqueous alcoholic media

The effect of ultrasonic irradiation (45KHz at 25°C) on the solvolysis of $\text{t}$-butyl chloride in aqueous ethanol, $\text{i}$-propanol and $\text{t}$-butanol is (1) to increase the rate constants in the more alcoholic media and (2) to reduce the m values of these reactions.     

Anionic tricarbonyl derivatives of molybdenum and tungsten and their reactions with allyl halides

A series of carbonylmetallate anions $\text{fac}$-[MX(CO)₃L₂]^?, where M = Mo or W, X = Cl, Br or I and L₂ = 1,10-phenanthroline(phen) or 2,2′-bipyridine(bipy) have been prepared from the corresponding $\text{cis}$-M(CO)₄L₂ complexes. No evidence of $\text{fac}$-to $\text{mer}$-isomerisation was evident on dissolution, although in MeCN solvolysis occurred with the formation of $\text{fac}$-M(CO)₃L₂(MeCN). Reaction of the anions with various allyl halides resulted in high yields of η³-allyl complexes [MX(CO)₂(η³-RC₃H₄)L₂]. The significance of these observations for the mechanism of the allyl oxidative-addition reaction are discussed.     

Mechanisms for reactions of halogenated compounds. Part 4.[1] activating influences of ring-nitrogen and trifluoromethyl in nucleophilic aromatic substitution

Rate constants have been measured for the reactions of ammonia with various fluorinated pyridines and diazines in aqueous dioxan at 25°. From the results the activating effects of ring-nitrogen (relative to CH) and of trifluoromethyl (relative to -H) have been determined. Ring-nitrogen activates the system at points $\text{ortho}$-, $\text{meta}$- and $\text{para}$- to the point of substitution, in the ratios $\text{ortho}$- 6.2 × 10⁴, $\text{meta}$- 8.5 × 10², and $\text{para}$- 2.3 × 10⁵. Similarly a trifluoromethyl substituent is activating by a factor of 2.4 × 10³$\text{ortho}$- and 4.5 × 10³$\text{para}$- to the point of substitution.     

Behavior of p-dimethylamino-α-bormostyrene and its dimer in dioxane-water

Monomeric $\text{p}$-dimethylamino-$\text{α}$-bromostyrene undergoes S_Nl increasingly slowly in 60 to 91% dioxane. Reaction is catalyzed by HClO₄, NaOH and NaClO₄. Dimer 11 reverts to monomer I in 91% dioxane. There is only a small solvent effect on the solvolysis rate of II.     

Nucleophilic participation in the solvolysis of the t-butyldimethylsulfonium ion

Studies with the $\text{t}$-butyldimethylsulfonium ion give evidence for nucleophilic participation in the solvolyses of $\text{t}$-butyl compounds but electrophilic assistance would be the dominant factor for $\text{t}$-butyl chloride solvolysis.     

Polar substituent effects in the solvolysis of 2-methyl-2-endo-norbonyl 2,4-dinitrophenyl ethers

The solvolysis rates of tertiary 2-endo-norbonyl derivatives $\text{2}$ are less strongly controlled by the polar effects of substituents at C(6) than the rates of the secondary analogues $\text{1}$.     

Vinyl cations 33 : 1-alkene-3-yne-2-yl triflates,precursors of triple bond stabilized vinyl cations - synthesis and first solvolytic studies.

The α-alkynyl vinyl triflates ($\text{3}$) are synthesized and the solvolyses reactions studied in different solvents. The solvolysis products and kinetic data indicate, that the hitherto unknown triple bond stabilized vinyl cation $\text{2a}$ ? $\text{2b}$ is formed as an intermediate.     

On the solvolysis of N-acetoxy-N-acetylaminobiphenyl: the complete lack of nitrenium ion involvement.

The solvolysis of N-acetoxy-4-acetylaminobiphenyl in 40% buffered aqueous acetone has been studied. Two processes have been identified, both leading exclusively to the formation of hydroxamic acid. By the use of 0-18 labeling, both have been shown $\text{not}$ to involve the intermediacy of nitrenium ions.     

Bridged and unbridged norbornyl cations

The solvolysis rates and products of 6-substituted 2-norbornyl-p-toluene-sulfonates $\text{1}$ and $\text{5}$ are controlled by 1,3-bridging, i.e. by the degree of bonding between C(6) and C(2) in the intermediate norbornyl cations.     

Fluoride in sea water: intercalibration study based on electrometric and spectrophotometric methods

Fluoride was shown to be a conservative constituent of sea water. Samples from the eastern tropical North Pacific, the Caribbean, the Labrador Basin, and the Reykjanes Ridge region indicated that the most probable $\text{F}\text{Cl}$ ratio in sea water is 6.71·10^-5 with an overall uncertainty of ±0.07·10^-5 based on 99% confidence limits of ±0.02·10^-5 and an allowance of ±0.05· 10^-5 for systematic error. Double-blind measurements from laboratories using electrometric and spectrophotometric methods agreed closely. Mean $\text{F}\text{Cl}$ ratios found were all within 0.7% of the most probable value.     

A pios study of the reaction Ne(3P2,0) + HCl → Ne + HCl+ (A2Σ+) + e−

The HCl⁺ (A) vibrational state distributions from the title reaction were studied over the 48–110 meV collision energy range. The $\text{1}\text{0}$ and $\text{2}\text{0}$ ratios increase by factors of about 1.3 and 2.5, respectively. The branching ratios appear to be determined primarily by Franck-Condon factors, and by the endoergicity of the ν′ = 2 level.     

Curve crossing in two excited states of IBr studied by photofragmentation

Curve crossing in two excited states of IBr was studied by means of photodissociation with a pulse dye laser. The ratios of the formed ground state Br(²P_{$\text{3}\text{2}$} and excited Br(²P_{$\text{1}\text{2}$}) were measured at various wavelengths. They are compared with ratios calculated with the Landau-Zener formula, using parameters given by Child. The agreement between the measurements and the calculations is very good.     

Reversibly-formed ion pairs are not involved during the solvolysis of N,O-diacetyl-N-arylhydroxylamines

Appropriate oxygen-18 labeling experiments demonstrate that N,O-diarylhydroxylamines do not undergo solvolysis $\text{via}$ the reversible formation of ion pairs. This is in total conflict with the conclusions from previous indirect kinetic studies of these ultimate carcinogen models.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.