Download Aldehydes and Ketones: Nomenclature, Synthesis, and Reactions and more Study notes Organic Chemistry in PDF only on Docsity! CEM 143 Summer 2009 Chapter 9 Study Guide Aldehydes & Ketones Generic Structure: R H O aldehyde R R' O ketone Nomenclature: Aldehydes: For acyclic molecules: 1) Define the longest alkane chain that contains the C=O 2) Remove “-e” ending of the alkane (e.g. methane becomes methan) 3) Add “-al” ending. For example: H3C H O 2 carbons so ethane --> ethan --> ethanal ethanal Common name: acetaldehyde H H O 1 carbon so methane --> methan --> methanal Common name: formaldehyde For cyclic molecules: 1) Use name of ring 2) Add “carbaldehyde” to end For example: H O H O Common name: benzaldehyde Ring = cyclohexane so full name is: cyclohexane carbaldehyde Ring = benzene so full name is: benzene carbaldehyde Ketones: For acyclic molecules: 1) Define the longest change that contains C=O 2) Remove “-e” ending (e.g. methane becomes methan) 3) Add numerical position of C=O , which gets priority in number over everything else we’ve learned so far 4) Add “-one” ending For example: R OH PCC R R' O 2o alcohol Ozonolysis: 1) O3 2) Zn, CH3COOH O O+ R' or CrO3, HCl Freidel Crafts Acylation of Benzene: Cl O AlCl3 O Reactions of Aldehyes and Ketones: This reaction is also review: R H O CrO3, HCl R OH O Addition to C=O: O !+ !" The C=O bond is polarized so the carbon (with the !+) acts as an electrophile (sink) Common Nucleophiles (sources) that add to carbonyls: H-OH H-OR H-CN M+ -C C R BrMg+ R- H3Al-H H2NR HNR2 !+ !" REAGENT ADDS OH OR CN C C R R H NR NR2 General Addition Reaction: O !+ !" Nuc- = Nucleophile (source) Nuc_ Nuc O- Tetrahedral intermediate (carbonyl carbon went from sp2 hybridized to sp3 so the shape went from trigonal planar to tetrahedral) Nuc OH This is the general way most addition reactions happen. For example: O !+ !" NC O- NC OH CN- HCN +H+ "cyanohydrin" O !+ !" O+ O- HO OH H-O-H H-O-H "hydrate or geminal diol" H H O !+ !" H3C O- H3C OH1) CH3MgBr "CH3 -" 2) H3O + O !+ !" H O- H OH1) LiAlH4 "H-" 2) H3O + This is a reduction reaction... it reduces the number of C-O bonds. NH2 H N N We figure out primary, secondary and teritary amines differently than we do alcohols and alkyl halides. primary amine secondary amine tertiary amine Primary amines have 1 non-hydrogen group attached to them, secondary amines have 2 non-hydrogen groups attached to them and tertiary amines have 3 non-hydrogen groups attached to them. Types of nitrogen compounds that work like the above reaction: O RNH2 N R H2NOH N OH hydroxyl- amine NH2NH2 N NH2 hydrazine N NHNH2 phenyl- hydrazine primary amine Acetal formation: General structure of an acetal: ORRO Acetals are ways to ‘protect’ carbonyls from reacting when you don’t want them to. How do we make acetals? We add some alcohol with an acid catalylst… O ROH, H+ ORRO This reaction proceeds just like imine fomation but with an extra few steps at the end! O ROH, H+ O + H ROH O H O+ RH Proton Transfer O+ H O R H O+ R ROH O R O+ R H -H+ O R O R Hemi- acetal - not stable! acetal Notice that all these steps are in equilibrium so they are reversible! By adding H2O and H + to the acetal we can go back to the ketone...+ H2O Cyclic Acetals:
