For each of the biological structures below state the type of inter molecular fo
ID: 1018027 • Letter: F
Question
For each of the biological structures below state the type of inter molecular force (dispersion, dipole - dipole, ion - dipole, hydrogen bonding) or use the term "hydrophobic effect" to indicate the reason mainly responsible for the structure. Presence of a - helix structure in some proteins Organization of phospholipids into lipid bilayers Shape distortion of red blood cells containing deoxyhemoglobin S Specificity of the base - pairs in DNA Insolubility of hydrocarbons in water Solubility of sodium chloride in water Order the following substances from lowest to highest expected boiling point Put the number of your choice on each line. Lowest HighestExplanation / Answer
3. presence of a-helix structure: Hydrogen bonding
Organization of phospholipids in lipid bilayers: Van der Waals forces and Hydrogen bonding
Shape distortion in red blood cells: Dispersion forces
Specificity of base pairing in DNA: Hydrogen bonding
Insolubility of hydrocarbons in water: Dispersion forces
Solubility of NaCl in water: ion-dipole interaction
b) Increasing trend of boiling point: CH4< CF4<CH3Cl<CH3OH
The trend depends on the intermolecular binding energy for each of these molecules. CH4, simple hydrocarbon contains only dispersion forces, the weakest of all intermolecular forces. Although in CF4, individual C-F bonds are highly polar, yet the overall molecule is non-polar, hence the intermolecular forces are weak. In CHCl3, the C-Cl bond is highly polar due to which there is a signficant dipole-dipole intermolecular interaction present, stronger than dispersion forces. And in CH3OH, other than the O-H polar feature which induces dipole-dipole interaction, there is strong intermolecular hydrogen bonding (strongest intermolecular interaction) present between O from one molecule with H from the other due to their electronegativity difference. Hence, with increasing intermolaecular forces the energy required to break them to turn into vapour phase from the liquid phase gets higher, and the boiling points also go up. That explains the given trend of increasing boiling points of those compounds.
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