Alcohols and Epoxides Flashcards
Alcohols
- Polar sp3-hybridised oxygen atom
- Creates a permanent dipole
- soluble in water and can form hydrogen bonds
Synthesis of alcohols
- Nucleophilic substitution on an alkyl halide
- Via Sn2 mechanism compete with elimination
- Markovnikov product more carbon cations (oxymercuration)
- Acid catalysed hydration with H+
Acetylide ion reacting with formalderhyde
Formation of primary alcohol
Reagent in Markovnikov
Boron
Reagent in AntiMarkovnikov
Mercuary
Organometallic compound
- Covalent bonds between carbon atoms and metal ions
- Has nucleophilic carbon atoms strong nucleophile
Grignard Reagents
- Groups are not acidic enough to be deprotonated by NaNH2
- When ketone or alderhyde is converted to alohol with another group
- Alkyl halide with magnesium metal in a anhydrous ether solution
Oxidation
- Loose H2 or adding oxidising agent
Reduction
- Loose O, O2 or X2 or adding reducing agent
Oxidation of primary alcohol reagent
- NaOCl or chromic acid H2CrO4
- Forms alderhyde
Oxidation of primary alcohol to alderhyde
- Dess–Martin periodinane
- NaOCl
- Forms carboxylic acid
Oxidation of alcohol in body Ethanol
- Ethanol reacts with the reagent NAD in the liver
- The alcohol dehydrogenase forms acetalderhyde
- then acetalderhyde reacts with NAD again and is oxidsed to acetic acid - not toxic
Markovnikov product
Acid-catalysed hydration with H2O
Oxymercuration–demercuration
Hg(OAc)2 followed by NaBH4
Chemical agents
- Disinfection on inanimate objects and antiseptic for human tissue
- Only few chemicalsagen achieve sterility
Factors that influence efficacy
- Kind of organism
- Degree of contamination
- Time of exposure
- Nature of the material treated
- Concentration of disinfectant
Synthesis of Alcohols from Alkenes
- Dihydroxylation synthesis add potassium manganite and hydroxyl ion
- Alkene turns to peroxyacid then to epoxide then carboxylic acid to alcohol
Organolithium Reagent
- Lithum reacts with halide to for organolithium reagent
- Strong nucleophiles and bases
Alcohol synthesis with Grignard reagent
- Formation of grignard where magnesium reacts with an alkyl halide in an anhydrous ether
- Grignard reagent attacks a carbonyl compound to form alkoxide salt
- After first reaction is complete water is added to protonate the alkoxide and give alcohol
- Alcohol with new Carbon-Carbon bond formed
Epoxide with organometallic reagent
- Nucleophilic displacement of epoxide forming a primary alcohol
Organometallic reagent with acid chloride and ester
- Both form tertiary alcohol
- Formation of unstable intermediate
- Formation of Ketone then alkoxide finally tertiary alcohol
Reduction of C=O synthesis of primary and secondary alcohol
- Hydride reagent add hydride ion reducing C=O to alkoxide ion
- Sodium Borohydride transfers a hydride ion to form carbon forming alkoxide
- Alcohol solvent protonates the alkoxide
Reduction of C=O using LiAlH4
- LAH transfers hydride ions to hydride ions forming an alkoxide ion
- After first reaction is complete water or diluted acid is added to protonate alkoxide
- Stronger than NaBH4 easily reducing ketones and alderhydes
- Reduces carbonyl groups and esters
Neither oxidation or reduction
- Add or loss of H+, -OH, and H2O
Oxidation and reduction can be identified by
- Counting the number of carbon oxygen bonds usually converting C-H to C-O
Alcohol reacting as weak nucleophile
- Forms into a strong nucleophile by loosing the hydrogen (Alkoxide ion)
- Alkoxide ion attack weak electrophile such as the alkyl halide
- Another way is weak nucleophile attacking a strong electrophile
Alcohol acting as an electrophile
- Poor electrophile turns to a good electrophile by loosing the hydrogen to produce water
- OH is a poor leavibng group needs to be converted to good leaving group
- OH bond broken off the hydrocarbon when reacting as electrophile
Formation of Tosylates
- Convert OH to a better tosylate leaving group
- Alkyl tosylate made from tosyl chloride
- P- toluenesulfonyl chrolide addition of pryridine base forming tosylate ester the bond is then broken
- Sn2 displacement of tosylate ion
- Formed in to diffrent functional group via Sn2 mechanism
Tosylate ester + Hydroxide ion
- Alcohol + tosylate ion
- (Must be unhindered primary or secondary alkyl group )
Tosylate ester + Cyanide ion
- Nitrile + Tosylate ion
- (Must be unhindered primary or secondary alkyl group )
Tosylate ester + Halide ion
- Alkyl halide + Tosylate ion
- (Must be unhindered primary or secondary alkyl group )
Tosylate ester + Alkoxide ion
- Ether + tosylate ion
- (Must be unhindered primary or secondary alkyl group )
Tosylate ester + Ammonia ion
- Tosylate ion +amine salt
- (Must be unhindered primary or secondary alkyl group )
Tosylate ester + LAH
- Alkane + Tosylate ion
- (Must be unhindered primary or secondary alkyl group )
Conversion of alcohol to alkyl halide (Hydrophilic acids HBr, HCl and HI
- Conversion of poor leaving hydroyl group to good leaving water group
- Protonation substitution Sn1 for 3 and 2 alcohol and for primary Sn1
Reaction with phosphorus halide
- Reaction with primary and secondary alcohol but not with tertiary
Dehydration reaction of alcohol
- Protonation of hydroxy group due to being poor leaving group
- Strong acid added forming water which is good leaving group and H2SO4
- Ionisation to a carbon cation slow step
- Deprotonation to give alkene fast step
- E1 elimination with tertiary and secondary not primary
Bimolecular condensation
- Nucleophile alcohol attacks electrophile via Sn2 displacement (primary alcohol) formation of an ether
Condensation
- Joins 2 or more molecules often with loss of a small molecule such as water under acidic dehydration conditions 2 reactions compete
Elimination
- Dehydration to give an alkene
Substitution
- Condensation to give an ether
Esterification of alcohol
(Fischer esterification)
- Alcohol + carboxylic acid = ester + water
Powerful way of forming an ester
- Alcohol + acid chloride = Ester (addition of pryodine to neutralise)
Inorgainc esters
- Alkoxy group replaces a OH of inorganic
Para-toluenesulfonyl chloride esterification
- Addition with alcohol and prydine forms tosylate ester and HCl
Formation of sulfate diester
- Sulphuric acid + alcohol = Sulphate ester
- Sulphate ester + alcohol = Sulphate diester
Formation of nitrate ester
- Nitric acid + alcohol = Nitrate ester and alcohol
Phosphoric acid esterification
- Can form triester phosphate 3 levels of esterification
Williamson ether synthesis
- Alkoxide ion is a strong nucleophilic base can react with primary alkyl halide and tosylate to form ether
- Leaving group can be a tosulate or a primary halide to form ether
- If alkyl halide is tosylate it is hindered by elimination
Ether formation
- From alkyl or aryl groups may be symetrical ether or unsymetrical
- Relatively unreactive and commonly used as a solvent
Epoxide
- 3 membered cyclic ether
- Used to add OH group to any compound as it is highly reactive
Synthesis of epoxide
- Alkene + Peroxyacid = epoxide + acid
- Base promoted cyclisation halohydrins
- Halohydrin + hydroxyl forms intermediate then epoxide which is an internal Sn2 reaction
Opening of epoxide via water
- Acid-Catalysed in water to form glycols
- Protonation of oxygen followed by Sn2 attack by water
Opening of epoxide via alcohol
- Protonation of oxygen forming good leaving group followed by alcohol attack Sn1 as alkocyl group bonds to more highly substitued carbon
Opening epoxide via hydrohalic acid
- Using a hydrogen halide forming a hydroylhalide then adding another hydrogen halide
Opening of epoxide with base catalyst
- Addition of either alcohol or hydroxide ion
- Attacking of the less hindered carbon atom in an Sn2 displacement
Opening of epoxides with organometallics
- R-MgX attacks epoxide by attacking least hindered carbon atom and R is bonded to the less substituted carbon
- Nucleophilic displacement of epoxide
