Ch 12 Terms: Alcohols from Carbonyl Compounds: Oxidation-Reduction and Organometallic Compounds

Dehydrogenation

(1) Oxidation of a compound by removing a pair of hydrogen atoms, H∙ , or by removing both a hydride ion, :H - , and a hydrogen ion, H+ (2) An elimination reaction that creates a double bond by removing a pair of hydrogen atoms, H∙ , from adjacent atoms

Jones oxidation

The use of chromic acid, H2CrO4 , and aqueous sulfuric acid in a solvent of acetone, to oxidize primary alcohols and aldehydes to carboxylic acids, and secondary alcohols to ketones, but it will not react with carbon-carbon double and triple bonds

Hydrogenation

(1) Reduction of a compound by adding a pair of hydrogen atoms, H∙ , or by adding both a hydride ion, : H- , and a hydrogen ion, H + (2) An addition reaction in which hydrogen adds to a double or triple bond, which is often accomplished through the use of a metal catalyst, such as platinum, palladium, nickel, rhodium, or ruthenium

Carboxylic acid

Molecule containing a carbonyl group, >C=O , that is attached to a hydroxyl group, -OH , which is called a carboxyl group, -COOH, with the general formula RCOOH.

Collins Oxidation

The use of a complex of chromium trioxide, CrO3 , and pyridine, C5H5N, in a solvent of dichloromethane, CH2Cl2 , to oxidize primary alcohols to aldehydes, and to oxidize secondary alcohols to ketones, but it will not react with carbon-carbon double and triple bonds

Carbanion

A chemical species in which a carbon atom bears a formal negative charge; the :C- anion has four sp3 hybrid orbitals with a lone pair of electrons in one of them, and it has a trigonal pyramidal molecular geometry; it can act as a Lewis base, a very strong Brønsted-Lowry base (pKa ≈ 50), and a powerful nucleophile. Common sources of ___________ are organolithium compounds, RLi, and Grignard reagents, RMgX.

Pyridinium chlorochromate, PCC

A complex formed when chromium trioxide, CrO3 , is dissolved in hydrochloric acid and then treated with pyridine, C5H5N. In a solvent of dichloromethane, CH2Cl2 , ____will oxidize primary alcohols to aldehydes, and it will oxidize secondary alcohols to ketones, but it will not react with carbon-carbon double and triple bonds.

Organolithium compound

A compound that contains a carbon-lithium bond, RLi, which is a common source of carbanions; it is formed by the reaction of lithium with an alkyl halide or aryl halide.

Organometallic compound

A compound that contains a carbon-metal bond

Carbonyl group

A functional group consisting of a carbon atom doubly bonded to an oxygen atom, >C=O

Protecting group

A group that is introduced into a molecule to protect a sensitive group, while the reaction is carried out at some other location in the molecule; the ____________ is later removed in a subsequent reaction.

Hydride ion

A hydrogen atom that has two electrons and a negative charge, :H- , which is a powerful nucleophile and a very strong base (pKa = 35); common sources of _________________ are lithium aluminum hydride, LiAlH4 , and sodium borohydride, NaBH4 .

Oxidation state (oxidation number)

A measure of the degree of oxidation of an atom in a substance, which is calculated as the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic, according to a set of rules

Sodium borohydride, NaBH4

A mild reducing agent that is usually used in an aqueous and/or alcohol solution; it reduces aldehydes and ketones into alcohols, but it will not reduce carboxylic acids or carboxylic derivatives, and it will not react with carbon-carbon double and triple bonds.

Carboxylic ester

A molecule containing a carbonyl group, >C=O , that is attached to an alcohol group, -OR' , with the general formula RCOOR' , which may be formed by the reaction of a carboxylic acid and an alcohol with the loss of water, H-OH. Also called an ester.

Aldehyde

A molecule containing a terminal carbonyl group, >C=O , that is attached to one hydrogen and one other carbon atom, with the general formula RCHO

Ketone

A molecule containing an internal carbonyl group, >C=O , that is attached to two other carbon atoms, with the general formula RCOR

Lithium aluminum hydride, LiAlH4

A powerful reducing agent that is usually used in an anhydrous ether solution, and followed by an aqueous acid work-up; it reduces carboxylic acids, carboxylic esters, aldehydes and ketones into alcohols, and it reduces amide, nitro, nitrile, imine, oxime and azide compounds into amines, but it will not react with carbon-carbon double and triple bonds.

Nucleophilic addition

A reaction in which a nucleophile adds to a substrate containing a polar multiple bond between carbon and a heteroatom (such as a carbonyl group, >C=O , or a nitrile group, -C≡N ); when a nucleophile attacks the δ+ carbon of a carbonyl group, an alkoxide anion intermediate is initially formed, which subsequently attacks an electrophile, such as H+

Reduction

A reaction that results in a gain of electrons, or that decreases the oxidation state of an atom in a molecule or ion. _______________ of an organic compound usually involves increasing its hydrogen content, decreasing its oxygen content, or removing a strongly electronegative atom.

Oxidation

A reaction that results in a loss of electrons, or that increases the oxidation state of an atom in a molecule or ion. __________ of an organic compound usually involves increasing its oxygen content, decreasing its hydrogen content, or adding a strongly electronegative atom.

Reducing agent

A substance that causes a decrease in the oxidation state of another substance; the ________________ is oxidized during the course of a reaction

Oxidizing agent

A substance that causes an increase in the oxidation state of another substance; the _____________ is reduced during the course of the reaction

Grignard reagent

An organomagnesium halide, RMgX, which is a common source of carbanions; it is formed by the reaction of magnesium with an alkyl halide or aryl halide.