Alkanes

Question 1

How can larger molecules minimise their cloud interactions?

Answer 1

Rotation occurs around carbon-carbon single bonds to also minimise electron cloud interactions.

Question 2

What are the different spatial arrangements of the atoms that result from the rotation around the sigma carbon-carbon bonds called?

Answer 2

Conformations.

Question 3

What are conformations?

Answer 3

The different spatial arrangements of the atoms that result from the rotation around the sigma Carbon-Carbon bond.

Question 4

What is a sawhorse representation?

Answer 4

A 3D representation of a molecule showing bonds

Question 5

What is a Newman projection?

Answer 5

A front-on view of the molecule, particularly of linear carbon chains, which will block the view of chain carbons, but show the arrangement of the branched chains.

Question 6

What is eclipsed conformation?

Answer 6

When the adjacent hydrogens are in line with each other (rather than separated at 60 degree angles)

Question 7

What is staggered conformation?

Answer 7

When the adjacent hydrogens are separated at a 60 degree angle.

Question 8

Which is the highest energy formation: eclipsed or staggered?

Answer 8

Eclipsed

Question 9

Which is the lowest energy formation: eclipsed or staggered?

Answer 9

Staggered

Question 10

Which is the most stable formation: eclipsed or staggered?

Answer 10

Staggered

Question 11

Which is the least stable formation: eclipsed or staggered?

Answer 11

Eclipsed

Question 12

What is steric strain?

Answer 12

The strain experienced by a molecule when groups are too close to one another causing their electron clouds to repel each other.

Question 13

What is steric strain also called?

Answer 13

Hinderance

Question 14

Why do organic chains tend to take a linear formation?

Answer 14

Any other orientation will result in atoms being close together, giving more steric strain and making the molecule less stable.

Question 15

If a conformation of a molecule is offset, but is not the most favourable, what is it called?

Answer 15

Gauche.

Question 16

What is the relationship between steric strain and stability?

Answer 16

Steric Strain decreases stability

Question 17

What do single bonds allow for in terms of the shape of a molecule?

Answer 17

Carbon-Carbon bond rotation allows the peptide to twist. How much or how little it twists is controlled by steric strain.

Question 18

What can flexible bonds do?

Answer 18

Rotate about single bonds.

Question 19

What are flexible molecules called?

Answer 19

Rotamers

Question 20

What is it called as a molecule rotates through bonds?

Answer 20

Conformational change

Question 21

What is a limitation of the stick-and-ball atom figures you make in science classes?

Answer 21

They are inaccurate because in truth the atoms are much, much closer than that (to scale)

Question 22

What is done to represent the carbon(s) you can’t see in a Newman Projection?

Answer 22

A circle is drawn around the front carbon.

Question 23

For the back carbon(s) in a Newman projection, where do you draw the lines from?

Answer 23

The circle, not the point.

Question 24

If you have a molecule with carbon branches extending from the main chain, how do you make it staggered?

Answer 24

The carbon chains must be opposite.