1- butanol, ionization

The ketone is added to a large excess of a strong base at low temperature, usually LDA in THF at -78 °C. The more acidic and less sterically hindered proton is removed in a kineti-cally controlled reaction. The equilibrium with a thermodynamically more stable enolate (generally the one which is more stabilized by substituents) is only reached very slowly (H.O. House, 1977), and the kinetic enolates may be trapped and isolated as silyl enol ethers (J.K. Rasmussen, 1977 H.O. House, 1969). If, on the other hand, a weak acid is added to the solution, e.g. an excess of the non-ionized ketone or a non-nucleophilic alcohol such as cert-butanol, then the tautomeric enolate is preferentially formed (stabilized mostly by hyperconjugation effects). The rate of approach to equilibrium is particularly slow with lithium as the counterion and much faster with potassium or sodium. 

There is a strong similarity between the mechanism shown m Eigure 5 12 and the one shown for alcohol dehydration m Eigure 5 6 The mam difference between the dehy dration of 2 methyl 2 butanol and the dehydrohalogenation of 2 bromo 2 methylbutane IS the source of the carbocation When the alcohol is the substrate it is the correspond mg alkyloxonmm ion that dissociates to form the carbocation The alkyl halide ionizes directly to the carbocation... 

The mass spectra of alcohols often completely lack a peak corresponding to the parent ion. This is due to extremely rapid loss of neutral fragments following initial ionization. For example, the mass spectrum of 2-methyl-2-butanol lacks a parent peak and contains strong peaks at M-15 (loss of CH3O and M-18 (loss of H2O). 

PIE curves for ra/z = 72 (C4H8O) measured in four butanol flames. The accepted ionization energies for species identified by the observed ionization thresholds are indicated. (From Yang, B. et at. Combust. Flame, 148,198, 2007. With permission.)... 

GC analysis for methanol, 1-propanol, 1-butanol, pyrrolidine, N-methylpyrrolidine, 2-pynolidinone, N-methyl-2-pyrrolidinone, gamma-butrolactone, dimethylsuccinate, and N-butyl-2-pyrrolidinone was performed with a Hewlett-Packard Model 5890 Gas Chromatograph equipped with a 30-meter, 0.53 mm I.D., 0.50-micron film, Nukol capillary column (Supelco, Bellefonte, PA) and a flame ionization detector (FID). 

The preparation of di-w-butyl ether is illustrative (Scheme 2.6). No reaction occurred with n-butanol alone for 2 h at 200 °C. However, in the presence of 10 mol % n-butyl bromide, 26% conversion of the alcohol to the ether was obtained after 1 h, without apparent depletion of the catalyst. It is known that addition of alkaline metal salts can accelerate solvolytic processes, including the rate of ionization of RX [41]. This was confirmed when the introduction of LiBr (10 mol %) along with n-butyl bromide, afforded a conversion of 54% after 1 h at 200 °C. Ethers incorporating a secondary butyl moiety were not detected, precluding mechanisms involving elimination followed by Markovnikov addition. 

Despite this superficial similarity, however, subtle differences between the behaviour of ionized amines and the analogous ionized alcohols and ethers remain. Thus, metastable ionized 2-butylamine loses 80% ethane in contrast, ionized 2-butanol eliminates both ethane (35%) and methane (40%)85. The latter reaction corresponds to loss of the smaller methyl group and an a-hydrogen atom from the larger ethyl substituent at the branch point. Methane loss does not occur from ionized amines with a methyl substituent on the -carbon, with the solitary exception of ionized isopropylamine which does expel methane (10%). However, ionized 3-hexylamine eliminates both ethane (35%) and propane (20%)85. 

McAdoo, D.J. Hudson, C.E. Ion-Neutral Complex-Mediated Hydrogen Exchange in Ionized Butanol a Mechanism for Nonspecific Hydrogen Migration. Org. Mass Spectrom. 1987, 22, 615-621. 

Traeger, J.C. Hudson, C.E. McAdoo, D.J. Isomeric Ion-Neutral Complexes Generated From Ionized 2-Methyl-propanol and n-Butanol the Effect of the Polarity of the Neutral Partner on Complex-Mediated Reactions. J. Am. Chem. Soc. Mass Spectrom. 1991, 3,409-416. 

The kinetics of the alkaline hydrolysis of 2-methylpentyl salicylate (24) have been studied in various aqueous propanol and r-butanol mixtures and in mixtures of water and ethane-l,2-diol. ° Further smdies of the aminolysis of ionized phenyl salicylate (25) have been reported, in which it was observed that, in mixed acetonitrile-water solvents, glycine, 1,2-diaminoethane and 3-aminopropanol all reacted as did simple amines, via an intramolecular general-base-catalysed process. ... 

A 30-mL flask containing 0.2 mL of TTX solution (250 MU) and 0.5 mL of 1.5 N NaOH is heated at 80-90 °C for 30 min to derive C -base from TTX (18, 25). After being cooled to room temperature, the reaction mixture is adjusted to pH 3-5 with 10% HCl and extracted 3 times with 2 mL of n-butanol. The combined extracts are evaporated to dryness under reduced pressure. The C -base in the residue is converted to the trimethylsilyl derivative in the presence of N,0-bis(trimethyl-silyl)acetamide, trimethylchlorosilane and pyridine (2 1 1). This derivative is then applied to GC-MS (Hitachi 063 gas chromatograph column (2 m x 3 mm I.D.), Chromosorb W coated with 3% OV-1, temperature 180-250 °C (5 °C/min) Hitachi RMU 6 MG mass spectrometer ionization voltage 70 eV, carrier gas helium). 

Heptafluoro- 1-butanol can be added postcolumn to give a final concentration of 0.1 % (v/v) to enhance ionization efficiency during electrospray. Typically, a 2% (v/v) solution in mobile phase is added at 50 pl/min to the HPLC column effluent at 1 ml/min. Addition of this reagent is optional. 

Cell concentration in the reactor effluent was estimated by optical density (OD) and cell dry weight method using a predetermined correlation between OD at 540 nm and cell dry weight. Acetone-butanol-ethanol (ABE) and acids (acetic and butyric) were measured using a 6890 Hewlett-Packard gas chromatograph (Hewlett-Packard, Avondale, PA) equipped with a flame ionization detector and 6 ft x 2 mm glass column (10% CW-20M, 0.01% H3P04, support 80/100 Chromosorb WAW). Productivity was calcu-... 

When an inorganic phosphate buffer or sodium hydroxide is present, without imidazole, only weakly acidic phenol of pKa 11.6 can be detected. Since the phenolic group is adjacent to anionic sulfonates of the AOT, ionization is weakened. / -Nitrophenol in the water pool is influenced primarily by electrostatic interaction between molecular imodazole (Im) and the anionic surfactant group. When excess imidazole (but not methanol or n-butanol) is added to the water pool, a fraction of the interfacial /mitrophenol is displaced into the water pool. 

The observed responses for bromide ions at mlz 79 and 81 are for (A) 2,3-dibromopropanol and (B) 1,4-dibromo-2-butanol used as an internal standard. These analyses were carried out by atmospheric pressure ionization mass spectrometry with negative ion detection. Samples were introduced by gas chromatography (5% SE-30 on 100-120 mesh Gas Chrom Q 1.8 m X 2 mm glass column 110°C isothermal nitrogen 40... 

The low Sn2 reactivity of 1°-alkyl bromide, 2,2-dimethyl-1-bromopropane (neopentyl bromide, 2.5), is explained by steric hindrance to the required 180° alignment of reacting orbitals. However, under Sn 1 conditions, neopentyl bromide (2.5) reacts at roughly the same rate as other 1°-alkyl halides such as ethyl bromide. Ionization of alkyl halides to carbocation in SnI is the rate-determining step. Although the product from ethyl bromide is ethanol as expected, neopentyl bromide (2.5) yields 2-methyl-2-butanol (2.6) instead of the expected 2,2-dimethyl-1-propanol (neopentyl alcohol) (2.7). This is because once formed the ethyl carbocation can only be transformed by a substitution or elimination process. In the case of the neopentyl carbocation, however, the initially formed l°-carbocation may be converted... 

For the preparation of LB films usually the subphase is water or em aqueous electrolyte solution. In some cases mixtures of water and other solvents (for exairriple, glycerol, ethanol and butanol) are used. When the monolayer consists of ionizable molecules, the pH and the concentration and valency of electrolyte ions in the subphase are important variables. An appropriate pH value keeps the molecules... 

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