TBBOL- Week 2

What is the definition of intramolecular?

Interactions taking place between separate parts of the same molecule.

What is the definition of intramolecular?

Interactions taking place between separate molecules.

What are some of the characteristics of covalent bonds?

High bond energies, strong bonds, short distances and high directionality.

What are some of the interactions that molecules and ions do without forming bonds?

LDF’s, PDI’s, steric repulsion, hydrogen bonds, ionic interactions and hydrophobic forces.

What are the three types of electrostatic interactions?

Charge-charge, charge-dipole and dipole-dipole.

What is a dipole?

A neutral molecule with an asymmetric internal distribution of charge.

What is an induced dipole?

A temporary dipole created in a non-polar molecule by the proximity of another charged ion or polar molecule.

What are dispersion forces?

The force of attraction between the two areas of opposite charge of two temporary dipoles.

How strong are induced dipoles?

They are very short-lived, they are extremely weak and they operate over a very short distance.

What is steric repulsion?

When two molecules approach each other, the electrons on their surface will repel each other.

What drives the aggregation of non-polar molecules in aqueous solutions?

Entropy.

What bond is a special type of dipolar interaction?

Hydrogen bond.

To which electronegative atoms does a hydrogen atom bond to?

Oxygen, nitrogen and fluorine.

What are some examples of where hydrogen bonds can be found in biology?

Proteins and nucleic acids.

What maintains the double-helix structure in DNA?

Hydrogen bonds.

Does water freeze from top to bottom or bottom to top and why does it do it this way?

Top to bottom and this is because of the strong directionality of hydrogen bonds.

What are some of the physical-chemical properties that affect hydrogen bonding?

Surface tension, viscosity and capillary action.

What are the two examples of intramolecular bonding in DNA?

Alpha helix and beta sheets.

What is the special name given to dipole-dipole interactions?

Keesom forces.

What are isomers?

Compounds with the same atomic composition but with different structural or stereochemical formula and hence different physical and/or chemical properties.

What are stereoisomers?

Molecules with the same structural formula, same atom connectivity, but different orientation of their atoms in space.

What are the two types of stereoisomers?

Geometric isomers and enantiomers.

What occurs because of the restricted rotation around a double bond?

Cis and trans isomers.

What are the respective letters for trans and cis isomers?

Trans are E and cis are Z.

What takes priority when it comes to deciding if a geometric isomer is trans or cis?

The atomic number.

What are enantiomers?

Pairs of molecules which are mirror images of each other and are non-superimposable.

What is the sterogenic centre?

A quaternary atom with four different substituents.

Is the presence of a stereogenic centre a sufficient condition for chirality?

No.

Are symmetrical molecules chiral or not chiral?

Non-chiral.

What property do chiral molecules have?

They are able to rotate the plane of polarised light.

What are the two configurations of a sterogenic centre?

Rectus and sinister (R & S).

What would the letter be if the direction of the substituents from 1-3 was anti-clockwise?

Sinister (S).

What law allows us to see if amino acids are L or D?

CORN law.

What are the four symmetry operations?

Rotation, reflection, inversion and identity.

What are the three symmetry elements?

Axis, mirror plane and point.

What does inversion involve?

Projecting each point through the centre of symmetry and out of the same distance on the opposite side.