Cycloalkanes

Question 1

Cycloalkane Def. Examples

Answer 1

Saturated hydrocarbons that have at least 1 ring. Eg cyclopropane (3 carbon ring), cyclobutane (4 carbon rings). Rings consist of at least 3 carbons, chain must lose 2 Hs to be converted to ring

Question 2

How to number carbons in chain

Answer 2

Moving in directio shortest between constituents from substituent alphabetically highest

Question 3

Cycloalkane stability factors

Answer 3

Angle strain, torsional strain and steric strain

Question 4

Ring/Angle Strain Outline

Answer 4

How much angles between C molecules differ from 109 degrees. The higher the divergence on either side = the higher strain. Has bigger effects on chains with less Cs

Question 5

Torsional Strain Outline

Answer 5

Strain when 2 carbon factors eclipse each other. High in ecplised molecules lowers the more distorted they are from eclipsed

Question 6

Steric Strain Outline

Answer 6

Strain due to electrostatic repulsion of atoms when they get close to each other

Question 7

Why Cyclohexane is so stable

Answer 7

Doesn’t experience angle or torsional strain. It can pucker (rotate) to form angles of 109 degrees and move out of eclipse formation (become staggered). Adopts confirmation that isn’t planar

Question 8

2 Confirmations of Cyclohexane

Answer 8

Chair (s-shape, more stable) and boat (u-shape, less stable)

Question 9

Cyclohexane Chair (s-structure) outline

Answer 9

Puckered, sytaggered. Optimal bond angles, minimal torsional strain. 2 different subsituent positions: axial (at angles to molecule midline) and equatorial ( ring on midline)

Question 10

Ring Flip Outline

Answer 10

Axial and equatorial groups swap positions (eg axial to equatorial), carbons follow moving up/down molecule (freely). Groups favour equatorial (lower energy, substituents are further apart)

Question 11

Example of natural chair confirmations

Answer 11

Glucose in cyclic pyranose form

Question 12

Cholic Acid

Answer 12

polycyclic cycloalkane. Major bile acis, lipid emulsifier. Allows lipid hydrolysis by pancreatic lipase

Question 13

Cis Confirmation

Answer 13

Substituents are on the same horizontal side. Form u-shape with bond

Question 14

Trans Confirmations

Answer 14

Substituents are on the opoosite horizontal sides. Form s-shape with bond

Question 15

Can cis and trans configurations interconvert

Answer 15

No. Not, without bond cleavage

Question 16

2 Types of Isomers

Answer 16

Structural (different bond patterns) and Stereoisomers (same bond pattern)

Question 17

3 Types of stereoisomers

Answer 17

Conformers (single bond, interconvertible), configurational optical isomers (not-interconvertable by bond rotation) and configurational geometric isomers (restricted rotation)