Acetic acid electrostatic potential

Relative strengths of acetic acid and chlorosubstituted acetic acids. Electrostatic potential maps of CHjCOj- and CCljCOj show that the electron-withdrawing effect of the chlorine atoms makes the oxygen atoms in CCIjCO " less negative and less basic than those in CHjCO -. 

The greater positive character hence the increased acidity of the O—H proton of 2 2 2 tnfluoroethanol can be seen m the electrostatic potential maps displayed m Figure 1 8 Structural effects such as this that are transmitted through bonds are called indue tive effects A substituent induces a polarization m the bonds between it and some remote site A similar inductive effect is evident when comparing acetic acid and its trifluoro derivative Trifluoroacetic acid is more than 4 units stronger than acetic acid... 

FIGURE 19 2 Attrac tions between regions of positive (blue) and negative (red) electrostatic potential are responsible for intermo lecular hydrogen bonding between two molecules of acetic acid... 

Electron delocalization in carboxylate ions is nicely illustrated with the aid of elec trostatic potential maps As Figure 19 4 shows the electrostatic potential is different for the two different oxygens of acetic acid but is the same for the two equivalent oxygens of acetate ion... 

FIGURE 19.3 The free W energies of ionization of ethanol and acetic acid in water. The electrostatic potential maps of ethoxide and acetate ion show the concentration of negative charge in ethoxide versus dispersal of charge in acetate. The color ranges are equal in both models to allow direct comparison. 

FIGURE 19.4 Electrostatic potential maps of (a) acetic acid and (b) acetate ion. The negative charge (red) is equally distributed between both oxygens of acetate ion. The color range is different for (a) and (b). 

Electrostatic potential map for acetic acid shows negatively-charged regions (in red) and positively-charged regions (in blue). 

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). 

Organic acids are characterized by the presence of a positively polarized hydrogen atom (blue in electrostatic potential maps) and are of two main kinds those acids such as methanol and acetic acid that contain a hydrogen atom bonded to an electronegative oxygen atom (O-H) and those such as acetone (Section 2.5) that contain a hydrogen atom bonded to a carbon atom next to a C=0 bond (Q=C-C-H). 

Electrostatic potential maps of the conjugate bases from methanol, acetic acid, and acetone are shown in Figure 2.4. As you might expect, all three show a substantial amount of negative charge (red) on oxygen. 

Acetanilide, electrophilic aromatic substitution of, 939-940 Acetate ion, bond lengths in, 43 electrostatic potential map of, 43, 53, 56, 757 resonance in, 43 Acetk acid, bond angles in, 755 bond lengths in, 755 dimer of, 755 dipole moment of, 39 electrostatic potential map of, 53, 55... 

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... 

To what extent do electrostatic potential maps constructed for neutral acids and bases reflect acid and base strengths If they do, one should be able to replace having to look at a reaction energy by the simpler and more intuitive task of looking at a property of a molecule. It is clear that electrostatic potential maps uncover gross trends, for example, the acidic hydrogen in a strong acid, such as nitric acid, is more positive than that in a weak acid, such as acetic acid, which in turn is more positive than that in a very weak acid, such as ethanol. 

As their name implies, carboxylic acids are acidic—they dissodate slightly in aqueous solution to give H30+ and a carboxylate anion. Carboxylic acids are much weaker than inorganic acids like HC1 or H2S04, however. The Ka of acetic add, for example, is 1.78 X 10-5 (pKa = 4.75), meaning that only about 1% of acetic acid molecules dissociate in a 1.0 M aqueous solution. Note in the following electrostatic potential map of acetic add that the acidic -OH hydrogen is positively polarized (blue). 

Because oxygen is more electronegative than either carbon or hydrogen, the C—O and O—H bonds are polar. The electrostatic potential plot of acetic acid in Figure 19.1 shows that the carbon and hydrogen atoms are electron poor and the oxygen atoms are electron rich. 

Electrostatic potential plot of acetic acid (CH3COOH)... 

Electrostatic potential maps of the conjugate bases of (a) methyl alcohol, (b) acetic acid, and (c) acetone. The oxygen atoms carry much of the negative charge in all three. 

Use SpartanView to compare electrostatic potential maps of formic acid (HCO2H), acetic acid (CHjCOsH), and pivalic acid [(CH3)jCC02H]. How is the -OH hydrogen different from the others ... 

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