Organic Chemistry Chapter 5/6 Definitions and Main Concepts

What is Racemic?

A racemic mixture is a mixture that has no α, since it is equal R and S, and the α's cancel out to 0

What does a -α mean?

Levorotatery (l)

What factors affect α, and need to be listed?

Temperature (T), Concentration (C), and Length of Tube (l)

What is the proper reagent for making a 1° or 2° alkyl iodide?

a solution of both P and I₂ atoms

What is A nucleophile and what is it's abbreviation?

It is the molecule that is attacking the substrate, abbreviated Nu:.

How many stereoisomers will a molecule have?

It will have 2^n, where "n" is the number of chiral carbons in a molecule

What are the 3 types of alkyl halide and how do you tell them apart?

primary (1°), secondary (2°), and tertiary (3°), and just like looking at the classification of carbon, you look at the carbon attached to the halogen and see how many carbons are attached to it, that number is your classification.

Can a R chiral molecule spin to the left or a S chiral molecule spin to the right?

yes, if the lowest of the 4 atomic numbers is on the wedge in a 3-D representation or a horizontal line on a fisher projection, then it is the opposite (so an R would spin left, and S would spin right).

How many ways are there to name an Alkyl Halide?

2: one is the normal way of naming organic molecules (2-iodo-propane), while the other is the standard naming convention (isopropyl iodide).

What is the best base for the Nu: of a SN₂ Reaction?

A Strong Base

What is the best base for the LG of a SN₁ Reaction?

A Weak Base

What is the best base for the LG of a SN₂ Reaction?

A Weak Base

What is the best base for the Nu: of a SN₁ Reaction?

A Weak Base

How does the steric nature of the Nu: affect a SN₂ reaction?

A better Nu: will be less bulky, or less steric

What makes a good SN₂ substrate?

A less steric substrate, want the electrophilic C to be a 1°

What is a Chiral molecule?

A molecule that has a different mirror image. (think of your hands)

What is an Achiral?

A molecule that has the same mirror image. (think of a piece of paper folded in half).

What is a Protic Solvent?

A solvent with Hydrogen Bonds

What is an Aprotic Solvent?

A solvent without Hydrogen Bonds

What is a good rule of thumb to remember in substituition chemistry?

A strong base will substitute for a weak one!

What is the best substrate for a SN₁ Reaction?

A tertiary (3°), substrate

What are the 3 recommended (well, mentioned in the video), aprotic solvents?

Acetonitrile, Acetone, and Dimethyl Sulfoxide (DMSO)

How do you make a bad LG of an SN₂ Reaction a good one?

Add a H+ ion, (an alcohol is usually a good additive!)

What is a Alkyl Halide?

An alkyl function group with a Halogen attached

What makes a good SN₂ Solvent?

An aprotic solvent.

How does charge of Nu: affect an SN₂ reaction?

An atom with a negative charge is a much better Nu: than an atom with a neutral charge. Will beat another Nu: choice when determing Nu:, no matter period/group relation

How can you use the periodic table to tell if an element will make a better Nu:?

As you move towards the left of the table, and for any in the same group, take the one farther down the table. so in short ← first, then ↓.

How do you tell which order to count the atoms in a molecule (for chirality)?

By looking at the atomic number, count highest to lowest. For example if the four groups are Cl, I, O, and H: I is highest at 53, then Cl at 17, O at 8, and H is counted last at 1.

What are the factors affecting an SN₂ reaction?

Charge of Nu:, Sterics of Nu:, Polarizerbility of Nu:, Solvent and Substrate

What is the α?

It is the angle the light rotated in a polarimeter

What does a +α mean?

Dexterotatory (d)

What is a Leaving group and it's abbreviation?

It is the atom or molecule that is being forced out of the compound. Abbreviated LG

Where does the arrow representing the leaving group mechanism need to go?

From the bond between the substrate and LG to the LG

Where does the arrow representing the substituting mechanism need to go?

From the electrons on the Nu: to the C on the substrate

What is the proper reagent for making a 3° alkyl bromide?

HBr, or Hydrobromic Acid

What is the proper reagent for making a 3° alkyl cloride?

HCL, or Hydrochloric acid

What is the proper reagent for making a 3° alkyl iodide?

HI, or Hydroiodic Acid

Easy way to tell if a C is chiral?

If it has 4 different groups bonded to it

How many sterioisomers will a meso molecule have?

It can be found using the formula: (2^n)-1, where n is the number of chiral carbons in the molecule.

What is a Meso molecule?

It is a stereo-isomer with 2 or more chiral carbons, but the total molecule has a plane of symmetry!

What is an easy way to see if a molecule is chiral or achiral?

Look for a plane of symmetry! If there is one, the molecule as a whole is not chiral! (although certain molecules in the larger molecule may be!)

What Happens if there is a tie in the atomic number when counting for chiral molecules?

Move to the next one until there is no tie.

What is the proper reagent for making a 1° or 2° alkyl bromides?

PBr₃, or Phosphorus Tribromide

what is ppl?

Plane Polarized Light, or light that will go through a polarimeter.

What are the two types of polar solvents?

Protic and Aprotic solvents

What are the two divisions of Stereo-isomers?

R and S

What are the two substitution reaction mechanisms that occur?

SN₁ and SN₂

What is the most common type of reaction in our reality?

SN₂ Reactions

What is the proper reagent for making a 1° or 2° alkyl cloride?

SOCL₂, or Thionyl Chloride

What is a diastereomer?

Stereo-isomers that are not mirror images

What is the polrizerbility of an Nu:? How does it effect the quality of the Nu:?

The ability of an atom to move it's e- cloud to steal from another molecue. The farther down the group, the better the molecule is as the Nu:, which is counterintuitive

What is the Substrate?

The molecule where the reaction takes place

What is an electrophilic site?

The partial positive charge on a C that makes it desirable to the Nu:

What would be the better substrate if both electrophilic C's are 2°?

The simplest molecule would be the better choice!

Enatomers

Two molecules that are mirror images but not superimposable

What is special about a Diastereomer?

The two molecules will have different properties

What is the relationship b/w two halogens on adjacent C's?

They are

What is the relationship b/w two halogens on the same C?

They are Geminal

What are R and S's relationship to each other?

They are mirror images

What makes a chiral molecule an R?

When counting the order of the elements, you go in a clockwise circle. (R= Rectus or to the Right)

What makes a chiral molecule an S?

When counting the order of the elements, you go in a counter-clockwise circle (S= Sinister or to the left)

How can you tell how toxic a alkyl halide is?

by looking at the number of halogens attached, the more halogens attached, the more dangerous the chemical is!

What is the importance of ppl?

if the solution is opitically active, or rotated through the polarimeter, the solution contains chiral molecules

Does an α being d or l mean the chiral molecule is S or R?

no, but the R will be opposite of S, and d will be opposite of l

How do you make alkyl halides?

the best way is to start with an alcohol version of the alkyl halide you want, and then add the appropriate reagent.