5. Alkanes

Question 1

List the types of bonds in terms of increasing ionic character…

Answer 1

Symmetrical covalent bond
Polar covalent bond
Ionic bond

Question 2

What does Valence Bond theory suggest?

Answer 2

The valence atomic orbitals (AOs) need to combine together to form bonds

Question 3

What is the problem with the valence bond theory?

Answer 3

The shapes and directions of the C atom valence AOs do not allow for the formation of a tetrahedral C atom in CH4

Question 4

What are conformational isomers?

Answer 4

When there is free rotation about a sigma bond, an infinite array of conformations is possible through rotation

A conformer is one specific conformation of a molecule

Question 5

What is the difference between staggered and eclipsed?

Answer 5

Staggered conformers are more stable (lower in energy) than eclipsed conformers, due to reduced steric interactions

Question 6

What is the most stable conformation of long chain Alkanes?

Answer 6

The most stable conformer of long chain alkanes is when all anti staggered conformations are adopted, leading to a characteristics zig zag or sawtooth structure

Question 7

What are lipids?

Answer 7

• Phospholipids are principle components of cell membranes (lipid bilayer)
• Contain long Alkanes chains that stack together
• Polar groups exposed to aqueous environment