Boiling points bonds

Biochemistry Boiling point Bond or chemical bond Buffer solution... 

Bohr Model Boiling point Bond energy Bony fish... 

The dotted lines represent hydrogen bonds. The high boiling point and viscosity of the pure acid indicate strong intermolecular forces of this kind. 

Table 14.2 shows that all three elements have remarkably low melting points and boiling points—an indication of the weak metallic bonding, especially notable in mercury. The low heat of atomisation of the latter element compensates to some extent its higher ionisation energies, so that, in practice, all the elements of this group can form cations in aqueous solution or in hydrated salts anhydrous mercuryfll) compounds are generally covalent. 

Hydrogen bonds between —OH groups are stronger than those between —NH groups as a comparison of the boiling points of water (H2O 100 C) and ammonia (NH3 —33 C) demonstrates... 

Solubility in Water Alkyl halides and alcohols differ markedly from one another m their solubility m water All alkyl halides are insoluble m water but low molecular weight alcohols (methyl ethyl n propyl and isopropyl) are soluble m water m all pro portions Their ability to participate m mtermolecular hydrogen bonding not only affects the boiling points of alcohols but also enhances their water solubility Hydrogen bonded networks of the type shown m Figure 4 5m which alcohol and water molecules asso ciate with one another replace the alcohol-alcohol and water-water hydrogen bonded networks present m the pure substances... 

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... 

Hydrogen bonding m carboxylic acids raises their melting points and boiling points above those of comparably constituted alkanes alcohols aldehydes and ketones... 

Section 20 8 Esters are polar and have higher boiling points than alkanes of compa rable size and shape Esters don t form hydrogen bonds to other ester molecules so have lower boiling points than analogous alcohols They can form hydrogen bonds to water and so are comparable to alcohols m their solubility m water... 

Some ortho substituted phenols such as o mtrophenol have significantly lower boiling points than those of the meta and para isomers This is because the intramolec ular hydrogen bond that forms between the hydroxyl group and the substituent partially compensates for the energy required to go from the liquid state to the vapor... 

The —OH group of phenols makes it possible for them to participate m hydrogen bonding This contributes to the higher boiling points and greater water solubility of phenolic compounds compared with arenes and aryl halides... 

Methyl salicylate is the methyl ester of o hydroxybenzoic acid Intramolecular (rather than mtermolecular) hydrogen bonding is responsible for its relatively low boiling point... 

Acroleki acetals have also been prepared ki high yields (66). The formation of the acetal requkes the careful control of reaction conditions to avoid additions to the double bond. Table 5 Hsts a variety of acroleki acetals that have been prepared and thek boiling points (68). 

The physical properties of hydrofluorocarbons reflect their polar character, and possibly the importance of intermolecular hydrogen bonding (3). Hydrofluorocarbons often bod higher than either their PFC or hydrocarbon counterparts. For example, l-C H F bods at 91.5°C compared with 58°C for n-Q and 69°C for Within the series of fluorinated methanes, the boiling point reaches a maximum for CH2F2, which contains an equal... 

The location of the hydroxyl and aldehyde groups ortho to one another in saUcylaldehyde permits intramolecular hydrogen bonding, and this results in the lower melting point and boiling point and the higher acid dissociation constant observed relative to -hydroxybenzaldehyde. 

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