Miles Down Organic Chemistry

Number of Carbons: 1

Methane CH₄

Number of Carbons: 2

Ethane C₂H₆

Number of Carbons: 3

Propane C₃H₈

Number of Carbons: 4

Butane C₄H₁₀

Number of Carbons: 5

Pentane C₅H₁₂

Number of Carbons: 6

Hexane C₆H₁₄

Number of Carbons: 7

Heptane C₇H₁₆

Number of Carbons: 8

Octane C₈H₁₈

Number of Carbons: 9

Nonane C₉H₂₀

Number of Carbons: 10

Decane C₁₀H₂₂

IUPAC Naming Convention Steps

• Step 1: Find the parent chain, the longest carbon chain that contains the highest-priority functional group

• Step 2: Number the chain in such a way that the highest-priority functional group receives the lowest possible numbers

• Step 3: Name the substituents with a prefix. Multiple of the same type receive di-, tri-, tetra, etc.

• Step 4: Assign a number to each substituent depending on the carbon to which it is bonded

• Step 5: Alphabetize substituents and separate number from each other by command and form words by hyphens

Alkane

Saturated hydrocarbon with no double or triple bonds C_nH_2n+2

• Naming: Named according to the number of carbons present following by the suffix -ane

Isopropyl

Sec-butyl

Tert-butyl

Isobutyl

Alkene

Contains a double bond. Use suffix -ene

Alkyne

Contains a triple bond. Use suffix -yne

Alcohol

Contains a -OH group. Use suffix -ol or prefix hydroxy-

• Have higher priority than double or triple bonds

Diol

Contains 2 hydroxyl groups

• Geminal: If on same carbon

• Vicinal: If on adjacent carbons

Carbonyl Group

C=O

• Aldehydes and ketones both have a carbonyl group

• The reactivity of a carbonyl is dictated by the polarity of the double bond

• The carbon has a δ+ so it is electrophilic

• Carbonyl containing compounds have a ↑ BP than equivalent alkanes due to dipole interactions

• Alcohols have ↑ BP than carbonyls due to hydrogen bonding

Aldehyde

Carbonyl group on terminal C, bonded to at least one H

Suffix -al

In rings: suffix -carbaldehyde

Ketone

Carbonyl group on nonterminal C, bonded to two alkyl chains

Suffix -one

Prefix oxo- or keto-

• Are less reactive toward nucleophiles because of steric hindrance and ⍺-carbanion de-stabilization

  • The presence of an additional alkyl group crowds the transition steps and increased energy

  • The alkyl group also donates e- density to the carbanion, making it less stable

Primary Alcohols

C attached to OH is only attached to 1 other C

Secondary Alcohols

C attached to OH is attached to 2 other Cs

Tertiary Alcohols

C attached to OH is attached to 3 other Cs

Primary Amines

N is only attached to 1 C

Secondary Amines

N is attached to 2 Cs

Tertiary Amines

N is attached to 3 Cs

Carboxylic Acid

The highest priority functional group because it contains 3 bonds to oxygen

• Suffix “-ioc acid”; Salts: -oate; Dicarboxylic Acids: -dioic acids

• Always terminal groups

Ester

Carboxylic Acid derivative where -OH is replaced with -OR

• The condensation products of carboxylic acids with alcohols

  • Given the suffix -oate

  • The esterifying group is written as a substituent, without a number

  • Cyclic esters = lactones; named by the number of carbons in the ring and the Greek letter of the carbon forming the bond with the oxygen

  • Triacylglycerols include three ester bonds between glycerol and fatty acids

Amide

Replace the -OH group of a carboxylic acid with an amino group that may or may not be substituted

• The condensation product of carboxylic acid and ammonia or an amine

  • Given the suffix -amide

  • The alkyl group on a substituted amide are written at the beginning of the name with the prefix N-

  • Cyclic amides = lactams; named with Greek letter of the carbon forming the bond with the N

Structural Isomers

• Share only a molecular formula

• Have different physical and chemical properties

Stereoisomers

Compounds with atoms connected in the same order but differing in 3D orientation

Chiral Center

Four different groups attached to a central carbon

2ⁿ Rule

n = # of chiral centers

# of stereoisomers = 2ⁿ

Conformational Isomers

Differ by rotation around a single (σ) bond

Cyclohexane Substitutients:

Equitorial

In the plane of the molecule

Cyclohexane Substitutients:

Axial

Sticking up/down from the molecule’s plane

Enatiomers

Nonsuperimposable mirror images

• Opposite stereochemistry at every chiral carbon

• Same chemical and physical properties, except for rotation of plane polarized light

Optical Activity

The ability of a molecule to rotate plane-polarized light

• d- or (+) = RIGHT

• l- or (-) = LEFT 

Racemis Mixture

50:50 mixture of two enantiomers

• Not optically active because the rotations cancel out

Meso Compounds

Have an internal plane of symmetry, will also be optically inactive because the two sides of the molecule cancel each other out

Diastereomers

Stereoisomers that are NOT mirror image

Cis-Trans

• A subtype of diastereomers

  • Differ at some, but not all chiral centers

  • Different chemical and physical properties

Relative Configuration

Gives the stereochemistry of a compound in comparison to another compound

• Ex. D and L

Absolute Configuration

Gives the stereochemistry of a compound without having to compare to other compounds

• Ex. S and R

Cahn-Ingold-Prelog Priority Rules

Priority is given by looking at atoms connected to the chiral carbon or double-bonded carbons

• Whichever has the highest atomic # gets highest priority

(Z) for Alkenes

Highest priority on same side

(E) for Alkenes

Highest priority on opposite sides

(R) and (S) for Stereocenters

A stereocenter’s configuration is determined by putting the lowest priority group in the back and drawing a circle from group 1-2-3

• (R): Clockwise

• (S): Counterclockwise

Fischer Projection

Vertical lines go to back of page (dashes); horizontal lines come out of the page (wedges)

Alternating Fischer Projection

Switching 1 pair of substituents inverts the stereochemistry

• Switching 2 pairs retains stereochemistry

• Rotating entire diagram 90° inverts the stereochemistry

• Rotating 180° retains stereochemistry

Do the compounds have the same molecular formula?

YES

Then they are Isomers

Do the compounds have the same molecular formula?

NO

Then they are different

Do the isomers have the same connectivity of atoms?

YES

Then they are stereoisomers

Do the isomers have the same connectivity of atoms?

NO

Then they are constitutional isomers

Does the interconversion of stereoisomers require breaking bonds?

YES

Then they are configurational isomers

Does the interconversion of stereoisomers require breaking bonds?

NO

Then they are conformers

Are the configurational isomers non-superimposable mirror images?

YES

Then they are enatiomers

Are the configurational isomers non-superimposable mirror images?

NO

Then they are diastereoisomers

Bonding Orbitals

Created by head-to-head or tail-to-tail overlap of atomic orbitals of the same sign

• ↓ energy  ↑ stable

Antibonding Orbitals

Created by head-to-head or tail-to-tail overlap of atomic orbitals of opposite signs

• ↑ energy  ↓ stable

Single Bonds

1 σ bond, contains 2 electrons

Double Bonds

1 σ and 1 𝜋

• Pi bonds are created by sharing of electrons between two unhybridized p-orbitals that align side-by-side

Triple Bonds

1 σ + 2 𝜋 

• Multiple bonds are less flexible than single bonds because rotation is not permitted in the presence of a 𝜋 bond

• Multiple bonds are shorts and stronger than single bonds, although individual 𝜋 are weaker than σ bonds

sp³ Hydridization

25% s character and 75% p character

• Tetrahedral geometry with 109.5° bond angles

sp² Hydridization

33% s character and 67% p character

• Trigonal planar geometry with 120° bond angles

sp Hydridization

50% s character and 50% p character

• Linear geometry with 180° bond angles

Resonance

Describes the delocalization of electrons in molecules that have conjugated bonds

Conjugation

Occurs when single and multiple bonds alternate, creating a system of unhybridized p orbitals down the backbone of the molecule through which 𝜋 electrons can delocalize

Lewis Acid

 e- acceptor. Has vacant orbitals or + polarized atoms

Lewis Base

e- donor. Has a lone pair of e-, are often anions

Bronsted-Lowry Acid

Proton donor

Bronsted-Lowry Base

Proton acceptor

Amphoteric Molecules

Can act as either acids or bases, depending on reaction conditions

K_a

Acid dissociation constant. A measure of acidity

• It is the equilibrium constant corresponding to the dissociation of an acid, HA, into a proton and its conjugate base

pK_a

An indicator of acid strength

• pKa decreases down the PT and increases with EN

• pKa = -log(K_a)

⍺-carbon

A carbon adjacent to a carbonyl

⍺-hydrogen

Hydrogen connected to an ⍺-carbon

Relatively acidic and can be removed by a strong base

• The e-withdrawing O of the carbonyl weakens the C-H bonds on ⍺-hydrogens

• The enolate resulting from deprotonation can be stabilized by resonance with the carbonyl

Nucleophiles

“Nucleus-loving”. Contain lone pairs or 𝜋 bonds

• They have ↑ EN and often carry a NEG charge

• Amino groups are common organic nucleophiles

Nucleophilicity

A kinetic property. The nucleophile’s strength

• Factors that affect nucleophilicity: charge, EN, steric hindrance, and the solvent

Electrophilicity

“Electron-loving”. Contain a + charge or are positively polarized

• More positive compounds are more electrophilic

Leaving Group

Molecular fragments that retain the electrons after heterolysis

• The best LG can stabilize additional charge through resonance or induction

• Weak bases make good LG

SN1 Reactions

Unimolecular nucleophilic substitution. 2 steps.

• Step 1: LG leaves, forming a carbocation

• Step 2: Nucleophile attacks the planar carbocation from either side, leading to a racemic mixture of products

• Rate = k [substrate]

SN2 Reactions

• Bimolecular nucleophilic substitution. 1 concerted step.

  • Nucleophile attacks at the same time as the LG leaves

  • Nucleophile must perform a backside attack, which leads to inversion of stereochemistry (R) and (S) is also changed if the nucleophile and LG have the same priority level

  • SN2 prefers less-substituted carbons because steric hindrance inhibits the nucleophile from accessing the electrophilic substrate carbon

  • Rate = k [nucleophile] [substrate]

Oxidation Number

Charge an atom would have if all its bonds were completely ionic

Oxidation

Raises oxidation state. Assisted by oxidizing agents

• Aldehydes and ketones are commonly produced by oxidation of primary and secondary alcohols, respectively

Oxidizing Agent

Accepts electrons and is reduced in the process

Reduction

Lowers oxidation state. Assisted by reducing agents

Reducing Agent

Donates electrons and is oxidized in the process

Chemoselectivity

• Both the nucleophile-electrophile and REDOX reactions tend to act at the highest-priority (most oxidized) functional group

• One can make use of steric hindrance properties to selectively target functional groups that might not primarily react, or to protect functional groups

Polar Protic Solvents

Can Dontate H+

Favor SN1 and E1

• Acetic Acid

• H₂O

• ROH

• NH₃

Polar Aprotic Solvents

Can’t Donate H+

Favor SN2 and E2

• DNF

• DMSO

• Acetone

• Ethyl Acetate

Methyl Substrate in Polar Protic Solvent, Polar Aprotic Solvent, Strong Small Base, and Strong Bulky Base will Undergo ___ Reaction(s)

SN2 for ALL of the above

• Methyl is too unstable to have carbocation from SN1

Primary Substrate in Polar Protic Solvent, Polar Aprotic Solvent, Strong Small Base, and Strong Bulky Base will Undergo ___ Reaction(s)

SN2: Polar Protic, Polar Aprotic, and Strong Small Base

• Primary Structures are too unstable to have carbocation from SN1

E2: Strong Bulky Base

• Carbon will not want to replaced LG with a large bulky Nu so it prefers the double bond

Secondary Substrate in Polar Protic Solvent, Polar Aprotic Solvent, Strong Small Base, and Strong Bulky Base will Undergo ___ Reaction(s)

SN1/E1: Polar Protic Solvent

• Substrate is positively charged

• Stabilized by the solvent so that’s why it is willing to do 2 steps instead of 1

SN2: Polar Aprotic Solvent

• O2 won’t be able to stabilize as well so it doesn’t want to be a carbocation (1 step is better)

E2: Strong Small Base and Strong Bulky Base

• Carbon will not want to replaced LG with a large bulky Nu so it prefers the double bond

• Too many Cs attached for it to be SN2 and bases will just help replace LG with double bond

Tertiary Substrate in Polar Protic Solvent, Polar Aprotic Solvent, Strong Small Base, and Strong Bulky Base will Undergo ___ Reaction(s)

SN1/E1: Polar Protic and Polar Aprotic Solvents

• Are able to stabilize carbocations so SN1 and E1 are okay

E2: Strong Small Base and Strong Bulky Base

• Carbon will not want to replaced LG with a large bulky Nu so it prefers the double bond

• Too many Cs attached for it to be SN2 and bases will just help replace LG with double bond

Substitution Reactions

Nu reacting

• Nu attacking molecules and replacing LG

• Pay attention to which solution it is taking place in

• SN1: 2 steps, LG leaves THEN Nu attacks

• SN2: 1 step, LG leaves AND Nu attacks in same step

Elimination Reactions

In a basic solution (base)

• Get rid of LG and replace with double bond

• E1: 2 steps, LG leaves THEN solution replaces it with double bond

• E2: 1 step, LG leaves AND double bond is formed in same step