Hydrogen bond angles length

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. 

Such a trend is very different from that obtained from the corresponding NMR study. Amide chemical shifts are closely related to the length of the N—H bond but not related to the Rn---o- This implies that the chemical shift value gives useful information about the length of the N—H hydrogen bond. It seems that the hydrogen bond angle ([Pg.840]

These results show that such behavior is governed not only by the hydrogen-bond length, but also by the hydrogen-bond angle. 

Linear chains of proteins have conformation angles of ( ) = -120° and j/ = 120°. Such chains may orient in a parallel or an antiparallel manner, and the hydrogen bond angles are close to 160°, with lengths of about 2-3 A (Fig. 9.2.5). Such intermolecular hydrogen bond chains lead to 3-pleated sheets, which are extremely insoluble in water and do not swell. They are favored when R is small (e.g.,HorCH3). 

The central proton is halfway between the two oxygen atoms of the water molecules, and the ion has C symmetry The hydrogen bonds have lengths of 199 pm and the 0-H bond angle is 174 - The structure probably represents the transition state in the autoprotolysIs of water in which a proton is transferred from one water molecule to a neighbouring one. 

Figure 29.11 The model of Henn and Kauzmann predicts that (a) increasing the temperature T stretches and bends the water-water hydrogen bonds, while (b) increasing the pressure p shortens and bends those bonds, x is the hydrogen-bond length and 6 is the hydrogen-bond angle. Source AR Henn and W Kauzmann, J Phys...

Figure 4 shows the measured angle of 105° between the hydrogens and the direction of the dipole moment. The measured dipole moment of water is 1.844 debye (a debye unit is 3.336 x 10 ° C m). The dipole moment of water is responsible for its distinctive properties in the Hquid state. The O—H bond length within the H2O molecule is 0.96 x 10 ° m. Dipole—dipole interaction between two water molecules forms a hydrogen bond, which is electrostatic in nature. The lower part of Figure 4 (not to the same scale) shows the measured H-bond distance of 2.76 x 10 ° m or 0.276 nm. 

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