Ch. 3 Flashcards
Acyclic Formula
Cn H2n+2
Cyclic Formulas
Cn H2n
Primary Carbon
Bonded to one C
Secondary Carbon
Bonded to two Cs
Tertiary Carbon
Bonded to three Cs
Quarternary Carbon
Bonded to four Cs
Constitutional Isomers
Differ in the way the atoms are connect to each other
IUPAC Rules
- FInd the longest chain of carbons and use it as the base
- Name the attached groups using the location of each alkyl group by the number of the Carbon it’s attached to
- Write alkyl groups in alphabetical order regardless of their position on the chain
Naming Alkyl Groups (1 Carbon to 5 Carbons)
Methane, ethane, propane, butane, pentane
Iso grouping
When the Cs form a triange
CH3
CH –
CH3
Newman Projections – Eclipsed
The two molecules are almost on top of each other. Causes steric crowding and is high in energy
Newman Projections – Staggered
The Hs are is spread out equally. Less steric crowding, lower in energy
Keq equation (energy)
Keq = 10 ^ (± (3/2)∆E)
What are the two Butane conformations and their angles?
Gauche (60° between methyls)
Anti (180º between methyls)
HIgher alkanes resemble ______ in their preference for _____ and _____ conformations about the carbon-carbon bonds
Butane, anti and gauche
Geometric Isomers
Same molecules connected to the same carbons, but one is cis and one is trans
Cis molecule
The methyl groups are on the same side of the molecule
Trans molecule
The methyl groups are on opposite sides of the molecule
Cyclopentane ring strain
27 kcal/mol
Cyclotetrane ring strain
26 kcal/mol
Cyclohexane ring strain
0 kcal/mol
Cyclopentane ring strain
6 kcal/mol
cycloheptane ring strain
6 kcal/mol
cyclooctane ring strain
9 kcal/mol
cyclododecacane ring strain
5 kcal/mol
Ring strain
A type of instability that exists when bonds in a molecule form angles that are abnormal
In a cyclohexane, all the molecules are ____ so all bond angles can be ____ so there is no strain
staggered, 109.5°
What directions do axial Hs on a chair conformation point?
Up and Down
Which is more stable – equatorial or axial
equatorial because it has less steric crowding
How do you interconvert two chairs?
switch axial and equatorial
If there is an X group in the ____ position, it’s less stable because of ________
axial; steric crowding
In cis/trans decaline is locked into one confomer, but a cis/trans decaline can ring flip
trans; cis
Fused rings
Share two adjacent carbon atoms and the bond between them
Bridged rings
Share two nonadjacent carbon atoms and one or more carbon atoms (the bridge) between them
Spirocyclic compounds
Two rings share only one carbon
What fusion does a cis or trans-decalin have? Which is more stable
The second ring is attached by two cis or trans bonds. Trans is more stable because the alkyls are equatorial
