Forces between molecules hydrogen bonding

In general aldehydes and ketones have higher boiling points than alkenes because they are more polar and the dipole-dipole attractive forces between molecules are stronger But they have lower boiling points than alcohols because unlike alcohols two carbonyl groups can t form hydrogen bonds to each other... 

Until surface contact, the force between molecules is always one of attraction, although this attraction has different origins in different systems. London forces, dipole-dipole attractions, acid-base interactions, and hydrogen bonds are some of the types of attraction we have in mind. In the foregoing list, London forces are universal and also the weakest of the attractions listed. The interactions increase in strength and also in specificity in the order listed. 

In the case of nonionic but polar compounds such as sugars, the excellent solvent properties of water stem from its ability to readily form hydrogen bonds with the polar functional groups on these compounds, such as hydroxyls, amines, and carbonyls. These polar interactions between solvent and solute are stronger than the intermolecular attractions between solute molecules caused by van der Waals forces and weaker hydrogen bonding. Thus, the solute molecules readily dissolve in water. 

The unusually high boiling points of HF, H20, and NH3 result from an unusually strong type of dipole force called a hydrogen bond. The hydrogen bond is a force exerted between an H atom bonded to an F, O, or N atom in one molecule and an unshared pair on the F, O, or N atom of a neighboring molecule ... 

Hydrogen bond An attractive force between molecules found when a hydrogen atom is bonded to N, O, or F, 238-240, 616... 

DCA forms canal inclusion compounds, known as choleic acids, which most frequently have the orthorhombic space group P212121, or less frequently Pl l. In such crystals the DCA molecules hydrogen bond to each other to form an extended bilayer structure, thereby creating a hydrophobic canal between adjacent bilayers. The guest molecules present in these canals therefore tend to be non-polar or moderately polar molecules such as aromatic compounds, alkenes, ketones and certain carboxylic acids 92). Since the bilayers are held together only by van der Waals forces the canals are able to adopt different dimensions to accommodate the variety of... 

The weaker the intermolecular forces between molecules in the liquid phase, the higher is the vapor pressure. Generally, hydrogen bonding and the cumulative dispersion forces in larger molecules are the most significant factors (see Table 13-3). In order of decreasing vapor pressure,... 

The major forms of van der Waals forces between molecules that are not bonded together are the permanent dipole-dipole interaction, the dispersion-induced temporary dipole interaction, and the hydrogen bond. They are short-range forces that operate only when two atoms or molecules are in close proximity. The Lennard-Jones potential of 6-12 is a model of this potential field ... 

Even between neutral molecules, hydrogen bonds are in fact quite strong forces. They are indeed strong enough to maintain strength in a variety of structures. These include ice and a vast range of other crystalline structures-in crystals. 

Hydrochloric acid is an example of a molecule that exhibits dipole-dipole forces between molecules. Hydrochloric acid is made of one hydrogen atom (H+) and one chlorine (Cl") atom. The chemical formula for hydrochloric acid is HCl. In this case, the hydrogen atom gives its electron to the chlorine atom to form a chemical bond. 

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