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Organic Chemistry Aldehydes and Ketones Chapter 17.

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Presentation on theme: "Organic Chemistry Aldehydes and Ketones Chapter 17."— Presentation transcript:

1 Organic Chemistry Aldehydes and Ketones Chapter 17

2 Aldehydes and Ketones  Carbonyl Group C=O  Present in aldehydes and ketones Aldehydes Ketones

3 Aldehydes  Aldehydes  Sometimes abbreviated RCHO  Contain at least one H connected to the C Aldehydes

4 Ketones  Ketones  Carbonyl C is connected to two alkyl groups  RCOR’ Ketones

5 Nomenclature  IUPAC –Suffix is “-al” for the aldehydes –Suffix is “-one” for the ketones –# indicates position of ketone

6 Nomenclature NOTE: Ketone, Not keytone From Yahoo Images

7 Nomenclature  An Aldehyde or Ketone takes precedence over any previously considered group

8 Nomenclature  Common names - aldehydes

9 Nomenclature  Common names - ketones –Some are always used - Others name each R group and end with “ketone”

10 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

11 Physical Properties  Aldehydes and Ketones –can form H bonds with water ! –solubility in water is about the same as alcohols yes!

12 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

13 How do you make Aldehydes?  Aldehydes from Oxidation of 1 o alcohols –Problem is over oxidation to ACID! Practice a couple …………..

14 How do you make Ketones?  Ketones from Oxidation of 2 o alcohols Practice a couple …………..

15 Oxidation of Aldehydes  Aldehydes are easily oxidized –KMnO 4 –K 2 Cr 2 O 7 –even air oxidation carboxylic acid!

16 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

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18 Reaction 1.Oxidation – Tollens Test - Benedicts Test 2.Reduction – Hydrogen addition – NaBH 4 reagent 3.Addition of Alcohols – hemiacetal/acetal and tautomerism

19 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

20 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+

21 Benedict’s Test Oxidation of Aldehydes  overall reaction Cu 2 O

22 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 + -

23 Addition of H 2  Reduction to Alcohols –Hydrogen gas and a catalyst (Ni, Pd, Pt) –Similar to alkene to alkane reduction B

24 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

25 Addition of H 2 using NaBH 4  Reduction to Alcohols –NaBH 4 does not allow the reaction of the carbon carbon double bond B

26 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

27 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

28 Addition of Alcohol - Acetals B Step 1 Step 2 + H 2 O

29 Formation of Acetals  Addition of R-OH –acid catalyzed, 2 moles of alcohol react B ?

30 Formation of Acetals  Addition of R-OH –acid catalyzed, 2 moles of alcohol react B Draw the Hemi

31 Formation of Acetals  Acetal reaction in equilibrium B

32 Formation of Acetals  Acetal reactions B ?

33 Formation of Acetals  Acetal reactions 1 o alcohol B ?

34 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

35 Formation of Acetals  Cyclic hemiacetals –Reacts with a 2 nd. molecule of alcohol –Results in a cyclic acetal 1 o alcohol B

36 Formation of Acetals  Which are hemiacetals / acetals? B 123 456 78910

37 Keto-Enol Tautomerism  Equilibrium that exists  Keto (carbonyl) to Enol (alkene/alcohol) B

38 Keto-Enol Tautomerism  Equilibrium called Tautomerism 1 o alcohol B Keto form (more stable) (less stable)

39 Keto-Enol Tautomerism  Equilibrium called Tautomerism 1 o alcohol B Most enols are less stable

40 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

41 Important Compounds  Acetaldehyde –bp 21 o C –Converted to trimer »3 units of acetaldehyde »called paraldehyde »once used as a hypnotic/sleep-producer B

42 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

43 Important Compounds   -chloroacetophenone –lachrymators »tearing of eyes, etc. –Used as a tear gas –Active ingredient in “Mace” B


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