Hydrogen bond drawing

Exercise 23-21 2,4-Pentanedione reacts with methanamine to give a product of composition CgHnNO that is an equilibrium mixture of three isomers. The nmr spectrum of the mixture indicates that all three isomers have strong hydrogen bonding. Draw the structures of the three isomers and indicate the nature of the hydrogen bonding. 

Propanediol, HOCH2CH2CH2OH, can form intramolecular hydrogen bonds as well as intermolecular hydrogen bonds. Draw a structure of 1,3-propane-diol that shows an intramolecular hydrogen bond. 

For each of the compounds in Question 11 that form hydrogen bonds, draw a diagram of the two molecules using a dotted line to indicate where the hydrogen bonding will occur. 

An enol of 2,4-pentanedione can form an intramolecular hydrogen bond. Draw its structure and explain why it occurs in substantially smaller concentration than 4-hydroxy-3-penten-2-one. 

For 0-H (and N-H) acids, the situation is different owing to the formation of strong hydrogen bonds between the acid and the base. Firstly, the hydrogen bond draws the molecules to distances which are much smaller than the sum of van der Waals radii. It can be assumed that the mean distance between two equilibrium positions of the proton in the system 0-H 0 is about 0.75 A. For a hydrogen bond, the dependence of the energy of the system on distance can be described by the Morse function,... 

Figure 2.6. The tetrahedral structures of ice (a), (fc) are planes through sheets of selected oxygen nuclei (open circles), hydrogen nuclei (shotm in the insert as solid circles) are not shown in the main drawing. The insert illustrates the overlap of oxygen line pairs and the hydrogen nuclei, thus forming the hydrogen bonds (dotted lines)...

Figure 2.7 (a) Illustration of the twist of (3 sheefs. Befa sfrands are drawn as arrows from the amino end to the carboxy end of the p strand in this schematic drawing of fhe protein thioredoxin from E. coli, fhe sfrucfure of which was defermined in the laboratory of Carl Branden, Uppsala, Sweden, fo 2.8 A resolution. The mixed p sheet is viewed from one of ifs ends, (b) The hydrogen bonds between the P strands in the mixed p sheet of fhe same profein. [(a) Adapfed from B. Furugren.]... 

Strategy For hydrogen bonding to occur, hydrogen must be bonded to F, O, or N. In (c), draw the Lewis structure first. 

The solubility (or insolubility) of different vitamins is of concern in nutrition. Molecules of vitamins B and C contain several —OH groups that can form hydrogen bonds with water (Figure 10.3). As a result, they are water-soluble, readily excreted by the body, and must be consumed daily. In contrast, vitamins A, D, E, and K, whose molecules are relatively nonpolar, are water-insoluble. These vitamins are not so readily excreted they tend to stay behind in fatty tissues. This means that the body can draw on its reservoir of vitamins A, D, E, and K to deal with sporadic deficiencies. Conversely, megadoses of these vitamins can lead to very high, possibly toxic, concentrations in the body. 

Due to its strong hydrogen bonds, in the vapor state hydrogen fluoride is found as short chains and rings. Draw the Lewis structure of an (HF)3 chain and indicate the approximate bond angles. 

What Do We Need to Know Already This chapter huilds on the introduction to acids and bases in Section J. It also draws on and illustrates the principles of thermodynamics (Chapters 6 and 7) and chemical equilibrium (Chapter 9). To a smaller extent, it uses the concepts of hydrogen bonding (Section 5.5), bond polarity (Section 2.12), and bond strength (Sections 2.14 and 2.15). 

Fig. 27.—Schematic drawing of a hyaluronan segment. Each disaccharide repeat has the potential to participate in four hydrogen bonds, 1 and 2 across the (1— 4). an< 3 and 4 across the (1— 3)-linkage.

Students can explain hydrogen bondings correctly, but have difficulties, to predict them from chemical formula and to draw conclusions concerning the physical properties of the substance. (Peterson et al., 1989 Ozmen, 2004)... 

Fig. 18.3 Ball and stick drawing of the centro-symmetric [H2NEt2]2Zr2Clio. Atom labels, bond distances and hydrogen bonds are labeled on the left side of the figure and Zr-CI-H-N hydrogen-bond angles are labeled on the right side of the figure.

FIG. 26 Optimized structure of a water monolayer on mica obtained from molecular dynamic simulations by Odelius et al. The water molecules and the first layer of sihca tetrahedra of the mica substrate are shown in a side view in the top. K ions are the large dark balls. The bottom drawing shows a top view of the water. Oxygen atoms are dark, hydrogen atoms light. Notice the ordered icelike structure and the absence of free OH groups. All the H atoms in the water are involved in a hydrogen bond to another water molecule or to the mica substrate. (From Ref. 73.)... 

Explain your answer and draw a molecular picture that shows the possible hydrogen bonds between HCl molecules. 

C12-0012. Draw a molecular picture illustrating the hydrogen bonds that form between a methanol (CH3 OH) molecule and water molecules in a dilute aqueous solution of methanol. 

C12-0025. Draw molecular pictures that show every type of hydrogen bond that exists in a solution containing methanol, water, and ammonia. 

Draw a line structure that shows the various ways in which water molecules form hydrogen bonds with a protein backbone. 

Begin by drawing a section of protein backbone. Because the problem asks only about hydrogen bonds to the backbone, the side chains are not involved in this problem and may be designated simply as R. 

C13-0090. One nucleotide and its hydrogen-bonded partner in double-stranded DNA is called a duplex. Identify the duplex formed by guanine and draw its structure. 

---