Test 2 (copy)

Chapter 5, 6, 7

Which functional group is shown? (R = rest of molecule, X = any halogen)

Alkane

Naming of alkanes

Add: -ane

Which functional group is shown? (R = rest of molecule, X = any halogen)

Alkene

Naming of alkene:

Add: -ene

Which functional group is shown? (R = rest of molecule, X = any halogen)

Alkyne

Naming of alkyne

Add: -yne

Which functional group is shown? (R = rest of molecule, X = any halogen)

Alcohol

Generalized abbreviation of alcohol:

ROH

Naming of alcohols:

Add: -ol

Generalized abbreviation of alkyl halide:

RCl

Generalized abbreviation of sulfide:

RSR

Which functional group is shown? (R = rest of molecule, X = any halogen)

Ether

Generalized abbreviation of ether:

ROR

Which functional group is shown? (R = rest of molecule, X = any halogen)

Epoxide

Generalized abbreviation of amine:

RNH2

Which functional group is shown? (R = rest of molecule, X = any halogen)

Haloalkane

Which functional group is shown? (R = rest of molecule, X = any halogen)

Aldehyde

Generalized abbreviation of aldehyde:

Which functional group is shown? (R = rest of molecule, X = any halogen)

Ketone

Generalized abbreviation of ketone:

Which functional group is shown? (R = rest of molecule, X = any halogen)

Carboxylic Acid

Generalized abbreviation of Carboxylic acid:

Which functional group is shown? (R = rest of molecule, X = any halogen)

Acid Anhydride

Generalized abbreviation for acid anhydride

Which functional group is shown? (R = rest of molecule, X = any halogen)

Ester

Generalized abbreviation for ester

Which functional group is shown? (R = rest of molecule, X = any halogen)

Amide

Generalized abbreviation for amide

Which functional group is shown? (R = rest of molecule, X = any halogen)

Acyl Halide

Generalized abbreviation for acyl halide

Which functional group is shown? (R = rest of molecule, X = any halogen)

Amine

Generalized abbreviation of Amine

RNH2

Which functional group is shown? (R = rest of molecule, X = any halogen)

Nitrile

Generalized abbreviation of nitrile:

RC(triple bond)N

Generalized abbreviation of nitroalkane:

RNO2

Which functional group is shown? (R = rest of molecule, X = any halogen)

Thiol

Generalized abbreviation of thiol:

RSH

IUPAC Nomenclature of Alcohols

Named by identifying the longest straight carbon chain containing the -OH group.

The -ane suffix is replaced with -anol

The location of the -OH group on the chain is designed by a number

What takes priority when numbering the Cs in IUPAC Nomenclature of Alcohols

Alcohol Takes Priority

Halogens has same priority as methyl groups

What is the IUPAC name?

2,2-Dimethyl-1-propanol

What is the IUPAC name?

2-chloro-2-methylpentane

What is the difference between Primary Alcohols, Secondary Alcohols, and Tertiary Alcohols

Primary - The C connected to the alcohol is connected to 1 other carbon

Secondary - The C connected to the alcohol is connected to 2 other carbons

Tertiary - The C connected to the alcohol is connected to 3 other carbons

Alcohol and alkyl halide boiling point increase with

Stronger van der Waals forces

• Dipole-dipole

• Dipole / induced-dipole

• Induced-dipole / induced-dipole

Other than intermolecular forces what effects the boiling point of alcohols?

Amounts of carbons in the main chain (more carbons higher boiling point)

Branching (increased branching decreased boiling point)

Small alcohol are _ in water

Small alcohols are soluble in water

(Methyl and ethyl are considered small)

Formation of an alkyl halide from an alcohol and hydrogen halide reaction

What kinds of alcohol are most reactive toward hydrogen halides

Tertiary most reactive

Hammond’s Postulate

If two states are similar in energy, they are similar in structure

Step of SN1 Reaction with an alcohol as a reactant

1. Alcohol protonation (OH bonds with H)

2. Carbocation formation (H2O leaves)

3. Anion reaction with carbocation

Carbocation

A molecule in which a carbon atom has a positive charge and three bonds

Hybridization of carbocation

sp2 hybridized (molecular geometry is trigonal planar)

pz orbital is empty and perpendicular to the bond

What type of carbocation is the most stabile

tertiary

In carbocations: alkyl groups provide _ inductive donation than hydrogens

In carbocations: alkyl groups provide MORE inductive donation than hydrogens

Hyperconjugation

‘Sigma bond to p orbital donation’

3 centers sharing 2 electrons

2 things that stabilize carbocations

• inductive donation by alkyl groups along the sigma bond

• hyperconjugation, a through space donation of electron density by bonds that are adjacent and parallel to the empty p orbital

SN1 reactions are fastest with what kind of alcohol?

Tertiary (it forms most stable carbocation)

Stereochemistry of SN1 mechanisms

Not stereospecific

(But an SN1 reaction gives products that partially invert. Leading to a mixture

of S and R products generally)

2 types of rearrangements in SN1 mechanism:

Hydride Shift

Methanide Shift (Alkyl Shift)

Hydride Shift

In an SN1 reaction after carbocation formation:

A hydrogen atom from a higher order carbon atom will shift to the charged carbon

Therefore the anion will bond to the higher order carbons

Makes it more stable

Methanide Shift (Alkyl Shift)

In an SN1 reaction after carbocation formation:

A carbon atom from a higher order carbon atom neighbors to charged carbon will shift to the charged carbon

Therefore the anion will bond to the higher order carbon, that is now charges

Makes it more stable

(only happens if the donating carbon is connect to 2 more carbons than the charged carbon)

In real life the SN1 reaction for forming alkyl halides is __ convenient

In real life the SN1 reaction for forming alkyl halides is _Not Always_ convenient

In SN1 Substitution Nucleophilic _

In SN1 Substitution Nucleophilic UNIMOLECULAR

In SN2 Substitution Nucleophilic _

In SN2 Substitution Nucleophilic BIMOLECULAR

SN2 reactions are for _ carbons only

SN2 reactions are for sp3 carbons only

Does not work on alkenyl or aryl halides

Label each part

Nucleophile

An atom or ion with lone pairs used to form bonds

• Lewis base

• Typically anionic (more negative is stronger)

• Charge balanced by metal cations (usually is a salt)

All _ _ are nucleophiles

All HALIDE ANIONS are nucleophiles

Leaving Groups

A group that is lost during a nucleophilic substitution or elimination

Often halogens

What makes a good leaving group

Size (the larger the halide the better the leaving group)

Weak Base (the weaker the base the better the leaving group)

The _ the base the better the leaving group

The WEAKER the base the better the leaving group

Electrophile

an atom or a molecule that seeks an molecule containing an electron pair available for bonding

Rate of an SN2 reaction affected by

The concentration of the electrophile and the nucleophile

Are intermediates formed during an SN2 reaction?

No

SN2 reactions are concerted

Steps of an SN2 reaction

A nucleophile makes a bond with the electrophilic carbon

Leaving group is pushed out

Inversion of configuration

Reversal of 3-D arrangement

Stereochemistry of SN2 reactions

Stereospecific

Inversion of configuration

Nucleophile attacks from the opposite side of leaving group

Back-side attack

What type of alkyl halide reacts the fastest in SN2 reaction?

Primary

Small

Nucleophilicity

Measure of a Lewis base’s (nucleophile) ability to perform a substitution

4 things that effect nucleophilicity

Charge (anion is more reactive than neutral analogue)

Acidity (if the same atom the more basic more nucleophilic)

Steric bulk (if the same anion the less steric bulk the more reactive)

Electronegativity (less electronegative the more nucleophilic)

Periodic trend of nucleophilicity across a row

Gets less reactive as you move to the right

Periodic trend of nucleophilicity down a group

Gets more reactive as you move down

Both SN1 and SN2 benefit from _ solvents

Both SN1 and SN2 benefit from polar solvents

SN2 reacts fastest with __ solvents

SN2 reacts fastest with APROTIC solvents

Protic solvents solvate nucleophiles too effectively

SN1 reacts fastest with __ solvents

SN1 reacts fastest with PROTIC solvents

Polar protic solvents like water, alcohol or hydrogen halides lower the transition state energy of SN1 reactions

Protic

A hydrogen bond donor

Why are sulfonates exceptionally good leaving groups

They are very weak bases so good leaving groups and poor nucleophiles

Retrosynthesis

a logical approach to finding a synthetic pathway and can be a first step in planning a synthesis

Alkene Nomenclature

• Replacing the -ane ending of the corresponding alkane with -ene

• The alkene corresponding to the longest continuous chain that includes the double bond is the parent chain

• Number in the direction that gives the doubly bonded carbons lower numbers (alcohols still have priority)

Z configuration of alkenes

The 2 groups ranked higher using the Cahn-Ingold-Prelog rules, are on the same side of the double bond (both up or both down)

Zame

E configuration of alkenes

The 2 groups ranked higher using the Cahn-Ingold-Prelog rules, are on the opposite sides of the double bond (one up or one down)

Epposite

Stability of alkenes

Number of substituents (the more substituents the more stable because Hyperconjugation)

Orientation (trans molecules are more stable than cis, E is more stable than Z)

Bulky group are more stable

Exception: in small and medium rings (less than 12 carbons) cis alkenes are more stable than trans

Polarity of alkenes is based on

the functional groups attached directly onto the alkene pi bond

since double bonds lack rotation, the polarity can be additive or cancel out depending on position

Zaitsev’s rule

The most branched alkene will form

Regioselectivity of alcohol dehydration

Stereoselectivity

A preference that the majority of the product molecules exhibit

The product that is easier to make will be made more often

E1 mechanism (alcohol dehydration) steps

1. Alcohol protonation (OH bonds with H)

2. Carbocation formation (H2O leaves)

3. A base takes a proton (H) from the carbocation

4. The 2 electrons from the proton from a double bond, forming the alkene

E2 mechanism (alkyl dehydrohalogenation) steps

1. Hydrogen removed by strong base, electrons used to form a double bond

2. Leaving group is pushed out

E2 mechanism features

Regioselective

Stereoselective

Doubling concentration of either reagent _ the rate in SN2

Doubling the concentration of either reagent doubles the rate

3rd degree alkyl halides react with:

• Go through SN1/ E1 in the absence of anionic nucleophiles

• Go through E2 with strong bases like alkoxide or hydroxide

Achiral

Molecules that can be superimposed on its mirror image