Exam 3 Flashcards
What happens to axial substituents when you do a chair flip?
They become equatorial substituents
What happens to equitorial substituents when you do a chair flip?
They become axial substiuents
What happens to up substituents when you do a chair flip?
They become down
What happens to down substituents when you do a chair flip?
They become up
What kind of substituents are these?
Axial Hydrogens
What kind of substituents are these?
Equatorial Hydrogens
Which confirmation group is preferred by groups and why?
Equatorial because there are no 1,3 diaxial van der waal repulsions
What is a syn addition?
Substituents get added to the same side
What is an anti addition?
Substituents get added to different sides
What is a substitution with retention of configuration?
The leaving group is on the same side as the nucleophile. The asymmetric carbons have the same configuration.
What is substitution with inversion of configuration?
Leaving group is on different side than nucleophile. Asymmetric carbons have different configurations
What stereochemistry is the addition of a halogen to an alkene? Why?
Anti-addition; When you make a halogen ion, you occupy 1 side of the face so the opposite side is only space available for another addition.
What are stereospecific reactions?
Reactions in which different stereoisomers of a starting material give differ stereoisomers of a product
What is the stereochemistry of a hydroboration-oxidation?
Syn Addition
What is the stereochemistry of oxymercuration-reduction?
Anti addition
What is the stereochemistry of a hydrogenation reaction?
Syn addition
To be an alcohol, the OH group has to be attached to what?
An sp3 carbon
What are the intermolecular forces?
- Van der Waal’s attraction
- Polarizability
- Permanent Dipoles
- Hydrogen bonds
What happens to the Van der Waal’s attraction with the surface area of the interacting electron cloud?
Van der Waals’s attraction increases with increasing surface area/molar mass
What is the relationship between Van Der Waals’s attraction and boiling point?
As VDW attraction increases, boiling point increases because the bond is stronger and therefore harder to break
What is polarizability?
The polarizability of a molecule is a direct measure of how easy it is to create a dipole moment in a molecule
What is the relationship between EN and polarizability?
The more EN the halogen, the less polarizability and therefore the weaker the VDW attraction
What is a hydrogen bond IMF?
An attraction between the H on one atom with an unshared electron pair on another
What is a protic solvent?
An H-bond donor
What does it mean if a solvent is a donor?
Lewis Base / electron donator
What high dielectric constant classifies a molecule as polar?
> 15 = polar
What is a polar solvent?
A polar solvent effectively separates, or shields ions from one another
What does the rule like dissolves like mean?
Molecules with similar IMFs can break & form new IMFs between the solute and solvent, therefore dissolving in one another
When do nucleophilic substitution reactions happen?
Occur with primary alkyl halides
If you make an alkene as a product, is the reaction substitution or b-elimination?
B-elimination
What is the a-carbon in a B-elimination reaction?
The carbon bonded to the halogen
When do B-elimination reactions occur?
Occur with tertiary alkyl halides
What kind of reactions do secondary alkyl halides undergo?
Both substitution & B-elimination
Which side does equilibrium favor?
Equilibrium favors side with the weaker base
What is a Sn2 reacton?
Substitution-Nucleophilic-Bimolecular.
A mechanism in which electron-pair donation by a nucleophile to an atom displaces a leaving group from the same atom in a concerted manner (occurs simultaneously)
What does bimolecular mean?
The rate-limiting step of the reaction involves 2 species
Which reaction is faster: Sn2 or Acid-Base?
Acid-base reactions occur instantaneously while most nucleophilic substitution reactions are much slower
What is a factor that influences the rate of Sn2 reactions?
The less branching there is on the alpha carbon and beta carbons, the faster the reaction will go.
