Acetic acid dimers

One after the other, examine methanol dimer and acetic acid dimer. Do the hydrogen-bond lengths in these systems differ significantly from the optimum distance in water dimer Are the hydrogen-bond angles in these compounds significantly different from those in water dimer Rationalize your results. 

Display an electrostatic potential map iot acetic acid. Where are the most electron-rich sites Where are the most electron-poor sites Propose a structure for the dimer of acetic acid based on favorable electrostatic interactions between electron-rich and electron-poor sites. Compare your structure to that for acetic acid dimer. What is another name for the types of interactions that hold the two acetic acid molecules together (See also Chapter 2, Problem 2). 

One after the other, examine structures for octane-1,8-dioic acid, nonane-1,9-dioic acid djud decane-1,10-dioic acid. Is there any difference (in structure or conformation) between the diacids with lower and higher melting points Which, if any, of the acids adopt structures similar to that of acetic acid dimer Account for the variation in melting points of these three compounds. 

DNA sequencing and. 1113 Electrospray ionization (ESI) mass spectrometry, 417-418 Electrostatic potential map, 37 acetaldehyde, 688 acetamide, 791,922 acetate ion. 43. 53, 56, 757 acetic acid. 53. 55 acetic acid dimer, 755 acetic anhydride, 791 acetone, 55, 56. 78 acetone anion, 56 acetyl azide, 830 acetyl chloride, 791 acetylene. 262 acetylide anion, 271 acid anhydride, 791 acid chloride, 791 acyl cation, 558 adenine, 1104 alanine, 1017 alanine zwitterion, 1017 alcohol. 75 alkene, 74, 147 alkyl halide, 75 alkyne. 74... 

Fig. 32. Packing relations and steric fit of the 26 acetic acid (1 1) clathrate (isomorphous with the corresponding propionic acid clathrate of 26)1U- (a) Stereoscopic packing illustration acetic acid (shown in stick style) forms dimers in the tunnel running along the c crystal axis of the 26 host matrix (space filling representation, O atoms shaded), (b) Electron density contours in the plane of the acetic acid dimer sa First contour (solid line) is at 0.4 eA" while subsequent ones are with arbitrary spacings of either 0.5 and 1 eA 3. Density of the enclosing walls comes from C and H atoms of host molecules.

Two solutions contain only sodium chloride, acetic acid, and water. In the first solution, the concentration of acetate ion is 0.0004 molar in the second, it is 0.0001 molar. The total ionic strength of each solution is 0.01. Compute the ratio of the activities of acetic acid in the two solutions. What can be said about the relative partial vapor pressures of the monomeric form of acetic acid above the solutions Of acetic acid dimer ... 

This may be further emphasized in that dffwatar for the acetic acid dimerization is very small [5, 6]. This conclusion has also been established for a number of other monocarboxylic acids in water from conductance and e.m.f. measurements (Table 1, [7]). 

Figures 3a and 3an show fs DFWM spectra of acetic acid (CH3COOH) and per-deuterated acetic acid (CD3COOD) vapor from a gas cell experiment (300K). In contrast to formic acid, acetic acid shows only J-type recurrences from dimeric species in the fs DFWM spectra at room temperature. The difference of 45 ps between the position in time of the recurrences from (CH-)C00H)2 and (CD3COOD)2 is determined by the smaller rotational constants B, C of (CD3COOD)2. From the non-linear fitting (Fig 3b, 3bo) the rotational constants A=5,7 0.3GHz B+C=1657.2 1.2MHz of the acetic acid dimer (CH3COOH)2 and...

A=5.4+0.4GHz B+C=1445.2 0.5MHz of the per-deuterated acetic acid dimer (CD3COOD)2 were extracted. It was not possible to determine the rotational constants B and C independently due to the symmetric prolate top nature of the dimeric structure (Ray s asymmetry parameter k=-0.965). More detailed consideration of the fs DFWM spectra taken in the gas cell and in a supersonic expansion for the acetic acid dimer are under way in our laboratory and will be presented in a forthcoming publication. 

Fig. 1. (a) OH stretching band of OH/OH (solid line) and OH/OD (dotted line) cyclic acetic acid dimers (inset) dissolved in CC14. (b) Change of absorbance AA of OH/OH dimers measured with parallel polarization of pump and probe for different delay times between pump and probe pulse. 

All data m the figures are for acetic acid monomer. In in-dustruil usage, acetic acid dimer is almost always present because of vapor phase dimerization The dimer has different phystcul properties which will affect the actual heat of vapor ination, vapor heal capacity, and vapor pressure. This has a significant effect on heal balances und distillation cukula tlons... 

Formic acid H.COOH and acetic acid CH3.COOH were studied in the crystalline state by Carlson, Witkowski and Fateley, 66> in the far infra-red region, while Fukushima and Zwolinski, 67> gave a normal coordinate calculation of acetic acid dimers (CH3.COOH)2 the acetate ion in Li(CH3.C00).2H20 was studied by Cadene 168>, while DiLauro, Califano and Adembri 169> studied the crystal spectra and normal modes of the anhydrides of maleic and succinic acids in polarized light. 

K. L. Wolf the term Ubermolekiile is coined to describe organised entities arising from the association of coordinatively saturated species (e.g. the acetic acid dimer)... 

Gaseous Acetic Acid Dimers CD3C02H and CH3C02H... 

Gaseous Acetic Acid Dimers CD3CO2H and CH3CO2H... 

Figure 20. The IR Vx-h line shapes of gaseous cyclic acetic acid dimers and isotope effect at room temperature.

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