CHEM 332 exam 3

Nucleophile

A Lewis base that forms a covalent bond by donating an electron pair to an electrophile. Usually has a negative charge, a pi bond, or a lone pair of electrons. Increases from right to left (C>N>O>Cl>F) and as you go down a column. Steric hindrance impacts the rate. In aprotic solvents, nucleophilicity mirrors basicity for the columns. F is more nucleophilic than Cl. sp-hybridized species are less nucleophilic than sp3-hybridized species.

Ozonolysis of Alkenes

An Alkene treated with O₃ , H₂O, and zinc. The result is the cleavage at the double bond, forming two carbonyl groups/

Hydration of alkynes

There are two forms, a markovnikov and anti markovnikov hydration. H₂SO₄, H₂O, and a catalyst (often times HgSO₄) leads to Markovnikov Hydration. Water adds across the triple bond, forming an enol. The enol then rapidly undergoes keto-enol tautomerization to form a ketone/aldehyde. In Anti-Markovnikov, a bulky borane (R₂BH) followed by H₂O₂ and NaOH leads to the water adding to the less substituted carbon.

Friedel-Crafts Acylation of aromatic compounds

A reaction used to attach compounds to a benzene ring. Uses benzene, an acetyl group ( a small chemical fragment with a C=O bond), and a catalyst (usually AlCl₃). The benzene ring lets the acetyl group attach and kicks off a hydrogen in itself. The result is an acetophenone and HCl.

Acyl Chlorides

Acid anhydrides acylate aromatic rings

Primary alcohols to aldehydes

requires a mild, anhydrous oxidizing agent, such as PCC (CH₂Cl₂), DMSO, and DMP.

Primary Alcohols to carboxylic acids

strong oxidizing agents, such as chromic acid (H₂CrO₄), sodium/potassium dichromate(Na₂Cr₂O₇), KMnO_{4, oxidize primary alcohols into R-COOH}

Secondary alcohols to ketones

Can only be oxidized once because the ketone lacks an extra alpha hydrogen. Both mild and strong oxidizing agents work for this conversion

Angle strain

when a molecule has bond angles that deviate from the ideal value, being 109.5 for alkanes

Carbonyl group

A molecule with coplanar geometry at an angle of 120 degrees. They are stabilized by alkyl substituenmts, so ketones are more stable than aldehydes. They have strong dipole-dipole forces with high boiling poitns (not higher than alcohols tho)

Hydroformylation (oxo process/synthesis)

An industrial chemical reaction that turns simple molecules into larger ones by adding a c-c chain extender. Uses an alkene, synthesis gas (CO and H₂), and a metal catalyst (like Rh and Cb). The result is a linear aldehyde

Carbonyl reduction to hydrocarbons

There are two methods, the Clemmensen reduction and Wolff-Kishner reduction

Clemmensen Reduction

Components: Zn(Hg) with aqueous HCl, and the carbonyl group. It works best in aromatic ketones under acidic conditions. The result is an alkene. Works identically for both aldehydes and ketones

Wolf-Kishner reduction

Components: A carbonyl compound, hydrazine (NH2NH2), a strong base (NaOH), polar protic solvent, and heat. The NH2 of hydrazone is deprotanated at high tempoeratures in the presence of a high base. The result is an alkene. The mechanism is identical for both ketones and aldehydes

Friedel-Crafts Alkylation

Components: a lewis acid (AlCl₃), an alkyl halide (double bonds or more are NOW allowed), and a benzene ring. The lewis acid attacks the halide, creating a carbocation. The benzene ring then attacks the carbocation. Carbon and hydrogen rearrangements WILL occur

Friedel-Crafts Acylation

Components: A lewis acid (AlCl₃), a benzene, and a carbonyl halide. The lewis acid abstracts the halide from the carbonyl compound. The benzene ring then attacks the carbocation. Rearrangements do NOT occur

Friedel-Crafts Workaround

Components: a Lewis acid (AlCl₃), a carbonyl halide, a benzene ring, followed by reduction. In order to avoid the rearrangements associated with alkylation, an acylation workup is followed by reduction to remove the carbonyl. The options for reduction include catalytic hydrogenation. clemmensen reduction, and wolff-kishner reduction

Nucleophilic Aromatic Substitution

Catalytic Hydrogenation of Carbonyls

Components: H₂, Lindlar’s Catalyst, high temperatures, and high pressures. There is an alcohol intermediate. If the substrate is a ketone on a benzylic position, it is fully reduced to an alkane. If not, it will be an alcohol

Reduction of Thioacetals

Components: a thioacetal, Lewis acid, and Raney nickel. The mechanism is somewhat mysterious, but the result is the carbonyl group being turned into a thioacetal, and then an alkane.