Presentation on theme: "Organic Chemistry Aldehydes and Ketones Chapter 17."— Presentation transcript:
Organic Chemistry Aldehydes and Ketones Chapter 17
Aldehydes and Ketones Carbonyl Group C=O Present in aldehydes and ketones Aldehydes Ketones
Aldehydes Aldehydes Sometimes abbreviated RCHO Contain at least one H connected to the C Aldehydes
Ketones Ketones Carbonyl C is connected to two alkyl groups RCOR’ Ketones
Nomenclature IUPAC –Suffix is “-al” for the aldehydes –Suffix is “-one” for the ketones –# indicates position of ketone
Nomenclature NOTE: Ketone, Not keytone From Yahoo Images
Nomenclature An Aldehyde or Ketone takes precedence over any previously considered group
Nomenclature Common names - aldehydes
Nomenclature Common names - ketones –Some are always used - Others name each R group and end with “ketone”
Physical Properties Carbonyls: Cannot form H bonding with each other: There is NOT an H connected to a F, N, O Aldehydes and Ketones are POLAR molecules and form dipole interactions Gives higher boiling and melting points
Physical Properties Aldehydes and Ketones –can form H bonds with water ! –solubility in water is about the same as alcohols yes!
Physical Properties Strong odors –Ketones generally have pleasant odors »perfumes, flavoring agents –Aldehydes odors vary »some pleasant cinnaminaldehyde, vanillin »some not pleasant formaldehyde Many are found in natural products http://www.youtube.com/watch?v=KDohVakqkic
How do you make Aldehydes? Aldehydes from Oxidation of 1 o alcohols –Problem is over oxidation to ACID! Practice a couple …………..
How do you make Ketones? Ketones from Oxidation of 2 o alcohols Practice a couple …………..
Oxidation of Aldehydes Aldehydes are easily oxidized –KMnO 4 –K 2 Cr 2 O 7 –even air oxidation carboxylic acid!
Oxidation of Ketones Ketones resist oxidation: –under mild or normal conditions, no reaction –more severe conditions yield mixtures –CO 2 and H 2 O under extreme conditions [O] This difference in reactivity can be used to Tell the difference between an aldehyde and ketone
Reaction 1.Oxidation – Tollens Test - Benedicts Test 2.Reduction – Hydrogen addition – NaBH 4 reagent 3.Addition of Alcohols – hemiacetal/acetal and tautomerism
Tollen’s Test The Silver Mirror Test Oxidation of Aldehydes Ag + ion in aq. ammonia NO reaction with KETONES Ag(NH 3 ) 2 + + aldehyde Silver Mirror Ag + + 2 NH 3 Ag(NH 3 ) 2 + Ag(NH 3 ) 2 + + RCHO Ag o + RCOO - + 4NH 3
Benedict’s Test Oxidation of Aldehydes Cu ++ ion, aqueous Orange to red ppt. NO reaction with KETONES Cu ++ + aldehyde Cu + (oxide) + acid Cu + Cu 2+
Benedict’s Test Oxidation of Aldehydes overall reaction Cu 2 O
Chemical Properties Addition to C=O –Other reactions are ADDITION Reactions –Bond is polar + and - –Negatives are attracted to C –Positives are attracted to O B + -
Addition of H 2 Reduction to Alcohols –Hydrogen gas and a catalyst (Ni, Pd, Pt) –Similar to alkene to alkane reduction B
Addition of H 2 Reduction to Alcohols –Will reduce ketones to 2 o alcohols –Slower reaction than reduction of C=C »C=C is reduced faster (first) if both C=O and C=C B
Addition of H 2 using NaBH 4 Reduction to Alcohols –NaBH 4 does not allow the reaction of the carbon carbon double bond B
Addition of Alcohol In the addition of R-OH to form an “acetal” the First step is the formation of a “hemiacetal” This is when an -OH and -OR are both on same C B
Formation of Acetals IF strong acid (HCl) is present, a second alcohol reacts to form the acetal (two -OR groups on C) B + H 2 O
Addition of Alcohol - Acetals B Step 1 Step 2 + H 2 O
Formation of Acetals Addition of R-OH –acid catalyzed, 2 moles of alcohol react B ?
Formation of Acetals Addition of R-OH –acid catalyzed, 2 moles of alcohol react B Draw the Hemi
Formation of Acetals Acetal reaction in equilibrium B
Formation of Acetals Acetal reactions B ?
Formation of Acetals Acetal reactions 1 o alcohol B ?
Formation of Acetals Hemiacetal reactions (formation of hemiacetals) –likely when within the same molecule 1 o alcohol B CH 2 2 2 2 O OH or HOHO O OOH a cyclic hemiacetal 1 1 2 2 3 3 45 5 4
Formation of Acetals Cyclic hemiacetals –Reacts with a 2 nd. molecule of alcohol –Results in a cyclic acetal 1 o alcohol B
Formation of Acetals Which are hemiacetals / acetals? B 123 456 78910
Keto-Enol Tautomerism Equilibrium that exists Keto (carbonyl) to Enol (alkene/alcohol) B
Keto-Enol Tautomerism Equilibrium called Tautomerism 1 o alcohol B Keto form (more stable) (less stable)
Keto-Enol Tautomerism Equilibrium called Tautomerism 1 o alcohol B Most enols are less stable
Important Compounds Formaldehyde –Gas at RT –Soluble in H 2 O –Formalin »37% formaldehyde »found in labs »preserves by denaturing proteins –Used to produce polymers B
Important Compounds Acetaldehyde –bp 21 o C –Converted to trimer »3 units of acetaldehyde »called paraldehyde »once used as a hypnotic/sleep-producer B
Important Compounds Acetone –bp 56 o C –Infinitely soluble in H 2 O –Excellent industrial solvent: »paints, varnishes, resins »coatings, nail polish –Produced in the body »diabetic ketoacidosis »“acetone breath” B
Important Compounds -chloroacetophenone –lachrymators »tearing of eyes, etc. –Used as a tear gas –Active ingredient in “Mace” B