CHEM 2443 UConn Exam 3

What is a racemic mixture?

A 1:1 mixture of enantiomers

How are enantiomers organized?

Pairs

What is an enantiomer?

A type of stereoisomer that are non-superimposable mirror images of each other.

What is a diastereomer?

A type of stereoisomer that are not mirror images of each other and have multiple chiral centers.

What is the favored conformation in chair if you have bulky groups?

Equatorial

What is a meso compound?

A compound that has a line of symmetry within itself and has opposite chiral centers, making it achiral

What are the two positions in chair conformation?

Axial and equatorial

What order does chair conformation flip in?

Chair, half chair, twist boat, boat, twist boat, half chair, chair

What direction does R go in

Right

What direction does S go in

Left

What is a stereoisomer?

A pair of molecules that have the same connectivity but different rotations in chiral centers

What is a constitutional isomer?

Isomers with different connectivities

What is a stereocenter?

A molecule which 4 different groups are attached and is asymmetric

How do you tell the difference between enantiomers?

Plane polarized light

How to calculate enantiomeric excess?

% Major enantiomer-% minor enantiomer

What is the name for separating a racemic mixture?

Enantiomeric resolution

What is stereochemical correlation?

Using reactions to tell the enantiomers from each other

What are enantiomers that are not asymmetrical?

Twist chirality

What are conformational enantiomers?

Enantiomers which rotate instead of making new bonds to become the other one, exists only in gauche not anti

What is amine inversion?

A pyramidal molecule flips, with only 2nd period molecules

What is the empirical formula of the cycloalkanes?

CH2

What is the most common cycloalkane?

Cyclohexane

What is a cis cyclohexane?

Both substituents up or down

What is a trans cyclohexane?

One up one down

What conformation does cyclopentane exist in?

Envelope

What conformation does cyclobutane exist in?

Puckered

What does cyclopropane exist as?

Planar, banana bonds

What is a bicyclic compound?

Two or more cyclic compounds connected by 2 or more bridge carbons

What is a spirocyclic compound?

A cyclic compound which is connected by one bridge carbon

What is it called when there is a carbon that is shared by two rings?

Bridgehead carbon

What is it called when carbons are not next to each other in a bicyclic compound?

Bridged bicyclic compound

What is it called when carbons are next to each other in a bicyclic compound?

Fused bicyclic compound

How do you name bicyclic compounds?

Bicyclo then numbers of bridges

What happens to trans decalin?

Conformationally locked

What is the first cyclic compound that can exist as trans?

Cyclononane

What is Bredt’s rule?

Cycloalkanes above 7 carbons can have a double bond at the bridgehead carbon

When do enantiomers start to act differently reaction?

When reacting with a chiral molecule

What is the rate difference between enantiomers

None

What is the rate difference in diastereomers?

Different for any molecule

Are enantiomers always racemic?

No

Are diastereomers always racemic?

Yes

What is syn addition?

Adding molecules to the same face

What is anti addition?

Adding molecules to different faces

What is inversion of configuration?

With replacement reactions, the molecule attaches from the other side and inverts the configuration

What addition with the bromonium ion

Syn

How is the bromide ion added to bromonium ion

Opposite-side substitution

How is hydroboration added?

Syn

How is BH3 added?

Syn concerted

What happens during the oxidation step of hydroboration-oxidation?

Stereospecific substitution, syn

How is oxymercuration?

Anti, highly regioselective but not stereoselective

What is an alcohol?

-OH

What is a thiol?

A molecule with a -SH group (mercapto or sulfhydryl)

What is a phenol?

Alcohol bonded directly to a benzene ring

What is a benzene ring/aryl group?

A 6 carbon ring with 3 double bonds

What is an enol?

An alcohol bonded to a carbon with a double bond, sp2 hybridized

What is an ether?

A molecule which has an oxygen connected to carbons

What is a sulfide?

Sulfur version of an ether

What is an alpha carbon?

The carbon bonded to the halogen in a alkyl halide or oxygen in an alcohol

How do you make the common name of alkyl halides?

Use the alkyl group then the halide name

How to make common name of alcohols?

Alkyl substituent and alcohol

What is a glycol?

A hydroxyl on both sides

How to name a thiol?

Alkyl and mercaptan

What is the principal group?

The group that determines suffix

How to name alcohols with more than one hydroxyl

diol, triol, etc

How to name ethers or sulfides common names?

Both alkyl groups then ether or sulfide

How to name ethers and sulfides IUPAC named?

Never principal group. Alkoxy or Alkylthio

What a molecule with a different molecule in a cyclic compound call

Heterocyclic

What is an epoxide

A two carbon one oxygen big ring

What is an induced dipole?

When a dipole is formed because theres another dipole nearby

What is van der waals interaction

Between dipoles

What is a protic molecule?

Hydrogen bond donors

What is an aprotic donor?

Cannot donate an h bond

How do polar molecules affect soluability?

Polar molecules have better solubility with ionic compounds

What is a miscible liquid?

A solvent that creates a solution no matter proportions

What is a xenobiotic compound?

A compound that does not occur in biology

What is a solvent shell?

Solvent molecules surrounding a solute

What is an ionophore?

Molecules that form complexes with ions

What are crown ethers?

Heterocyclic ethers with evenly spaced oxygens

What is a node?

A place where there is no chance of an electron being

What is the bond angle of a linear molecule?

180

What is the bond angle of a bent molecule?

>109.5

What is the bond angle of a trigonal planar molecule?

120

What is the bond angle of tetrahedral molecules

109.5

What is the bond angle of trigonal pyramidal molecules?

>109.5

What is a lewis acid?

An electron acceptor

What is a lewis base?

An electron donator

What is a bronstead-lowry base

a proton acceptor

what is a bronstead lowry acid?

A proton donor

What is a heterogeneous catalyst?

Exists in different states

What is a homogenous catalyst?

Exists in solution

What catalyst allows H2 addition?

Metal Pt/C

What does lindlar catalyst do? Pd/C

Allows H2 addition to alkynes

What is acid catalyzed hydration?

Acid catalyzes the addition of OH and H across the molecules

What is Markinov addition?

The most important group will bond to the most substituted carbon atom

What is a halonium ion?

A halogen both is attacked by a double bond but also acts as a nucleophile to the carbon, creating a bond to both carbons that were part of the double bond. This is more stable than a carbocation

How does the halonium ion turn into a regular halogen?

The leaving group from the last reaction attacks the partial positive charge of the carbon, and a bond from the attached halogen gives electrons back to the halogen

How is a halohydrin formed?

A halonium ion is formed, then in extreme excess water reacts with the carbocation. Then another water ion reacts with the hydrogen on the water, which gives the electrons back to the oxygen and it is now a hydroxyl group.

What is the most common halohydrin?

Vicinal

How is oxymercuration done?

Mercuric acetate attacks the carbon while the bond also attacks the mercury, and the bond from the mercury and the acetate part breaks. Then there is a positive charge which water attacks. the leaving group from before attacks the hydrogen on the water and through the addition of sodium borohydrate, the mercury is replaced with a hydrogen