Ethanol Atomic charges

TABLE 3.8 Atomic Charges" of Formic Acid, Ethanol, and Their Conjugate Bases... 

The force field for ethanol [252] consists of three LJ 12-6 sites plus three point charges and was parameterized to ab initio and experimental data. The nucleus positions of aU ethanol atoms were computed by QM at the HF level of theory with a 6-3IG basis set. This force field is also based on the anisotropic approach of Ungerer et al. [130]. The LJ parameters and the anisotropic offset were fitted to experimental saturated liquid density, vapor pressure, and enthalpy of vaporization. The simulation results from this ethanol force field deviate on average from experimental values of vapor pressure, saturated liquid density, and heat of vaporization by 3.7, 0.3, and 0.9%, respectively. 

The Claisen condensation is initiated by deprotonation of an ester molecule by sodium ethanolate to give a carbanion that is stabilized, mostly by resonance, as an enolate. This carbanion makes a nucleophilic attack at the partially positively charged carbon atom of the e.ster group, leading to the formation of a C-C bond and the elimination ofan ethanolate ion, This Claisen condensation only proceeds in strongly basic conditions with a pH of about 14. 

Dissolve ca. 0 2 g. of product (I) in cold ethanol, and add with shaking 1-2 drops of dilute sulphuric acid. A deep purple coloration appears at once. This shows that salt formation has occurred on the quinoline nitrogen atom to form the cation (Ha), which will form a resonance hybrid with the quinonoid form tils). [Note that the forms (IIa) and (11b) differ only in electron position, and they are not therefore tautomeric.] If, hoAvever, salt formation had occurred on the dimethylaniino group to give the cation (III), thrs charge separiition could not occur, and the deep colour would be absent. 

An active-site zinc ion stabilizes negative charge development on the oxygen atom of acetaldehyde, leading to an induced partial positive charge on the carbonyl C atom. Transfer of the negatively charged hydride ion to this carbon forms ethanol. 

Zinc-Copper Couple A 500-ml Erlenmeyer flask equipped for magnetic stirring is charged with a mixture of zinc powder (49.2 g, 0.75 g-atom) and hydrochloric acid (40 ml of 3 % aqueous solution). The contents of the flask are rapidly stirred for 1 minute, and the liquid is decanted. Similarly, the zinc is washed with the following three times with 40 ml of 3% hydrochloric acid solution, five times with 100 ml of distilled water, five times with 75 ml of 2 % aqueous copper sulfate solution, five times with 100 ml of distilled water, four times with 100 ml of absolute ethanol, and five times with 100 ml of absolute ether. These last ethanol and ether washes are decanted onto a Buchner funnel to prevent loss. The residue is collected by suction filtration, washed again with anhydrous ether, and dried in air. Finally, the zinc-copper couple is stored (20-24 hours) in a vacuum desiccator over phosphorous pentoxide. 

A 3-1. three-necked flask, equipped with a Dry Ice condenser (Note 1), a sealed Hershberg-type stirrer, and an inlet tube, is set up in a hood and charged with 108 g. (0.75 mole) of a-naphthol (Note 2). The stirrer is started, and to the rapidly stirred flask contents (Note 3) is added 11. of liquid ammonia as rapidly as possible (about 5 minutes). When the naphthol has gone into solution (about 10 minutes), 20.8 g. (3.0 g. atoms) of lithium metal (Note 4) is added in small pieces and at such a rate as to prevent the ammonia from refluxing too violently (Note 5). After the addition of the lithium has been completed (about 45 minutes), the solution is stirred for an additional 20 minutes and is then treated with 170 ml. (3.0 moles) of absolute ethanol which is added dropwise over a period of 30-45 minutes (Note 6). The condenser is removed, stirring is continued, and the ammonia is evaporated in a stream of air introduced through the inlet tube. The residue is dissolved in 1 1. of water, and, after the solution has been extracted with two 100-ml. portions of ether, it is carefully acidified with concentrated hydrochloric acid. The product formed is taken into ether with three 250-ml. extractions, and then the ether extract is washed with water and dried over anhydrous sodium sulfate. The ether is removed... 

A. 1,2-Dimethyl-l,4-cyclohexadiene. Caution This step should he conducted in a hood to avoid exposure to ammonia fumes. A 5-1. three-necked flask, cooled in a dry ice-isopropyl alcohol bath, is fitted with an efficient stirrer and a dry ice condenser. The flask is charged with approximately 2.5 1. of liquid ammonia, the stirrer is started, and 450 g. of anhydrous diethyl ether, 400 g. (10 moles) of absolute ethanol, and 318.5 g. (3.0 moles) of u-xylene (Note 1) are added slowly in that order (Note 2). I hen 207 g. (9.0 g. atoms) of sodium is added in small jtieees over a 5-hoiir... 

The apparatus used is shown in Fig. 2 (Note 1). A solution of sodium ethoxide prepared by dissolving 2.5 g. of clean sodium metal (0.11 gram atom) in 230 g. (292 ml., 5 moles) of absolute ethanol under anhydrous conditions is added to the reaction tube C. The tube C thus charged is weighed, and placed in position with the gas inlet tube, fitted with fritted-glass dispersion cylinder D, extending nearly to the bottom. Several inches of ethanol is placed in the tube G, which serves as a flow indicator. The... 

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