Organic Chemistry - Chapter 10: Alchohols

Alchohol

molecule with hydroxyl (OH) functional group

Physical Properties of Alcohol

unusually high boiling points due to hydrogen bonding and miscibility for only small alcohols with water due to their polar nature

Acidity of Alcohols

generally weak acids, (from ability to donate a proton (H+) from the hydroxyl group) much lower than water’s; more halogens, more acidity; more alkyls, less acidity

Acidity of Phenols

100 million times more acidic than cyclohexanol due to resonance stability

Formation of Sodium Alkoxides Reaction

an irreversible reaction where alcohols react with sodium to form alkoxides and hydrogen gas; used as nucleophile (Williamson ether synthesis), as a strong base in organic reactions (deprotonation), and in E2 elimination reactions to form alkenes

Formation of Sodium Alkoxides Reagents

alcohol (R-OH) + sodium metal (Na) or sodium hydride (NaH)

Formation of Sodium Alkoxides Products

primary alcohol (strong nucleophile - RONa⁺) + hydrogen gas

Formation of Potassium Alkoxides Reaction

an irreversible reaction where alcohols react with potassium to form alkoxides and hydrogen gas; used as nucleophile (Williamson ether synthesis), as a strong base in organic reactions (deprotonation), and in E2 elimination reactions to form alkenes

Formation of Potassium Alkoxides Reagents

alcohol (R-OH) + potassium metal (K) or potassium hydride (KH)

Formation of Potassium Alkoxides Products

secondary & tertiary alcohols (strong nucleophiles - ROK⁺) + hydrogen gas

Formation of Phenoxide Ion Reaction

phenol reacts with sodium hydroxide to form phenoxide ions; used in the synthesis of ethers and esters (Williamson Synthesis, Nucleophilic Aromatic Substitution)

Formation of Phenoxide Ion Reagents

phenol + strong base (sodium hydroxide (NaOH) or potassium hydroxide (KOH)) for deprotonation

Formation of Phenoxide Ion Products

phenoxide ion (C₆H₅O^-) + water (H₂O)

Organometallic Reagents

partial positive charge (metal) + partial negative charge (carbon) equals polarized C-M bond and electrophilic carbon

Limitations of Organometallic Reagents

no water or other acidic protons (to avoid protonation) and no other electrophilic multiple bonds (C=N, C—N, S=O, or N=O)

Grignard Reagents

made from reaction of alkyl halide + magnesium metal with ether solvent; heavier halide = greater reactivity

Organolithium Reagents

made from an alkyl halide with lithium with ether, alkanes, or non-protic solvents

Grignard + Organolithium reagents

can both produced from (1, 2, 3) alkyl, vinyl (−CH=CH₂), or aryl (cyclic) halides

Carbonyl Nucleophilic Addition Reaction

a nucleophile (Grignard reagent) attacks the electrophilic (_⁺) carbonyl carbon, forming an alkoxide ion intermediate

Carbonyl Nucleophilic Addition Reagents

ether (for intermediate) + diluted alcohol (H₃O⁺ - protonates intermediate to product)

Synthesis of 1° Alcohols (Single Addition) Reaction

grignard reagent + formaldehyde & ether + diluted alcohol = primary alcohol with one additional carbon

Synthesis of 2° Alcohols (Single Addition) Reaction

grignard reagent + aldehyde & ether + diluted alcohol = secondary alcohol

Synthesis of 3° Alcohols (Single Addition) Reaction

grignard reagent + ketone & ether + diluted alcohol = tertiary alcohol

Acid Chloride (Multiple Addition) Reaction

grignard attacks the acid chloride, chloride ion leaves, second mole of Grignard reacts with the ketone intermediate to make alkoxide ion

Acid Chloride (Multiple Addition) Products

alkoxide ion protonated with diluted alcohol to produce tertiary alcohol

Ester Addition Reaction

grignard attacks carbonyl, alkoxide ion leaves, second mole of Grignard reacts with the ketone intermediate to make alkoxide ion

Ester Addition Product

tertiary alcohol

Ring-Opening with Ethylene Oxide Reaction

grignard (strong nucleophile) attacks ethylene oxide (weak electrophile) forming alkoxide ion, alkoxide ion is protonated by dilute acid to make alcohols

Ring-Opening with Ethylene Oxide Products

primary + secondary alcohols

Carbonyl Reduction Reaction

hydride ion from the reducing agent attacks the electrophilic carbonyl carbon, forming an alkoxide intermediate which is protonated by a solvent or acid

Carbonyl Reduction Reagents

hydride reagents: sodium borohydride (NaBH₄) and lithium aluminum hydride (LiAlH₄)

Sodium Borohydride

only reacts with carbonyl of aldehyde or ketone (more selective)

Lithium Aluminum

stronger reducing agent – reacts with carbonyl of aldehyde, ester + carboxylic acids for primary alcohols and ketone for secondary alcohols

Carbonyl Reduction Products

primary + secondary alcohols

Catalytic Hydrogenation Reaction

reduces a ketone or an aldehyde to an alcohol by adding H₂ with Raney nickel catalyst (Raney Ni) (also reduces C-C double bonds)

Thiols

sulfur analogues of alcohols (-SH) instead of (-OH); more acidic than alcohol; larger size helps sulfur withstand negative charges

Thiol Synthesis Reaction

SN2 reactions of sodium hydrosulfide + unhindered alkyl halides producing a thiol (R-SH)

Thiol Oxidation Reaction

thiol groups (-SH) are converted to oxidized forms like disulfides (R-S-S-R') and sulfonic acids (R-SO₃H)

Thiol Oxidation Reagents

disulfides: 2RSH (two thiol molecules) + oxidizing agent (Br₂;Zn, HCl or O or peroxide)

sulfonic acids: KMnO₄ or nitric acid (HNO₃)

Thiol Oxidation Products

disulfides: R-S-S-R + Br or H₂O

sulfonic acids: R-SO₃H - expanded octet and charge separation