Aldehydes and Ketones Chapter 5

Aldehydes and Ketones Functional group is O Functional group is O The carbonyl l l group C group C Aldehyde = Carbonyl group is 1° Ketone = Carbonyl group is 2°

Aldehyde RCHO ArCHO Benzaldehyde

Ketones RCORArCOAr ArCOR O C – C-C-C C – C-C-C

Naming Aldehydes Drop –e from alkane and add –al Drop –e from alkane and add –al Methanal Propanal 2-chlorohexanal

Practice

Naming Ketones (2 ways) 1. IUPAC - # chain from the end closest to the carbonyl, give the carbon #, drop –e add –one 2. Name the groups on either side of the carbonyl and follow with ketone  list groups by order of sixe of molar mass (smaller 1 st )

Practice 2-butanone methyl ethyl Ketone 3-hexanone ethyl propyl ketone Draw 2 – pentanone and name it the 2 nd way

Practice For the “old” way to name a ketone to use a phenyl, the ring must be bonded directly to the carbonyl For the “old” way to name a ketone to use a phenyl, the ring must be bonded directly to the carbonyl3-phenyl-3-propanone ethyl phenyl ketone 4-phenyl – 3 – butanone/no secondary name

Practice

Preparation of Aldehydes 1. Oxidation of 1° Alcohols (lose H 2 ) RCH 2 OH PCC CH2Cl2 RCHO + H 2 RCH 2 OH PCC CH2Cl2 RCHO + H 2 Catalysts are PCC = Pyridinium chororchrmate, C 5 H 6 NCrO 3 Cl Dichloromethane = CH 2 Cl 2

Practice Form Propanal by oxidation Form Propanal by oxidation CH 3 CH 2 CH 2 OH  CH 3 CH 2 CHO + H 2

Practice 2. Oxidize 1-hexanol O C-C-C-C-C-C-OH  (Catalyst) C-C-C-C-C-C-H + H 2 + H 2 CH 3 (CH 2 ) 4 CH 2 OH  (Catalyst) CH 3 (CH 2 ) 4 CHO + H 2 + H 2

Practice Synthesize propanal (str) Synthesize propanal (str) C-C-C + Cl 2  C-C-C-Cl + HCl C-C-C-Cl + H 2 O  C-C-C-OH + HCl C-C-C-OH  (Catalyst) C-C-C=O + H 2

The 2 nd Reaction Type 2. Reduction of acid chlorides (add H 2 ) + H 2  (Pt/Pd) + HCl + H 2  (Pt/Pd) + HCl RCOCl + H 2  (Pt/Pd) RCHO + HCl * Acid chlorides look like aldehydes, but have a –Cl where the end –H is. (We will look at them more closely later)

Practice Form propanal by reduction Form propanal by reduction CH 3 CH 2 COCl + H 2  (Pt/Pd) CH 3 CH 2 CHO + HCl

Synthesis of Benzaldehyde The =O is not directly on the benzene, so you can’t follow he steps for an alcohol – you have to use the following… The =O is not directly on the benzene, so you can’t follow he steps for an alcohol – you have to use the following…

Synthesis of Benzaldehyde + -AlCl 3  + HCl + -AlCl 3  + HCl + 2Cl 2  + 2HCl + 2Cl 2  + 2HCl + H 2 O  + 2HCl + H 2 O  + 2HCl

Preparation of Ketones 1. Oxidation of 2° alcohols OH O OH O R-C-R’  (Catlaysts) R-C-R’ + H 2 RCHOHR’  (Catlaysts) RCOR’ + H 2

Practice Oxidize 2-pentanol (str, cond, name product) Oxidize 2-pentanol (str, cond, name product) OH O OH O C-C-C-C-C  (Catalyst) C-C-C-C-C + H 2 2-pentanone/methyl propyl ketone CH 3 CHOH(CH 2 ) 2 CH 3  (Ctlyst) CH 3 CO(CH 2 )2CH 3 + H 2

Practice Form methyl ethyl ketone (str, cond, name reactant) Form methyl ethyl ketone (str, cond, name reactant)

Practice Synthesize 3-heptanone (cond.) Synthesize 3-heptanone (cond.) CH 3 (CH 2 ) 5 CH 3 +Cl 2  CH 3 CH 2 CHCl(CH 2 ) 3 CH 3 + HCl CH 3 CH 2 CHCl(CH 2 ) 3 CH 3 + H 2 O  CH 3 CH 2 CHOH(CH 2 ) 3 CH 3 + HCl CH 3 CH 2 CHOH(CH 2 ) 3 CH 3  (Cats) CH 3 CH 2 CO(CH 2 ) 3 CH 3 + H 2

The 2 nd Reaction Type 2. Friedel – Crafts Acylation - acyl group RCO O O O O ArH + R-C-Cl –AlCl 3  R-C-Ar + HCl ArH + RCOCl –AlCl 3  RCOAr + HCl Benzene must bond directly to the C=O

Practice Form ethyl phenyl ketone (str, cond) Form ethyl phenyl ketone (str, cond) C-C-C-Cl + -AlCl 3  C-C-C- + HCl CH 3 CH 2 COCl + C 6 H 6 –AlCl 3  CH 3 CH 2 COC 6 H 5 + HCl Form pentyl phenyl ketone (str, cond)

Rxns of Aldehydes and Ketones 1. Reduction of aldes and kets to alcohols O R-C-H + H 2 –Pt/Pd  R-C-OH RCHO + H 2 –Pt/Pd  RCH 2 OH O O O O R-C-R + H 2 –Pt/Pd  R-C-R RCOR + H 2 –Pt/Pd  RCHOHR

Practice Reduce 2-hexanone (str,cond, name prod) Reduce 2-hexanone (str,cond, name prod) O OH O OH C-C-C-C-C-C + H 2 –Pt/Pd  C-C-C-C-C-C 2-hexanone 2-hexanone CH 3 CO(CH 2 ) 3 CH 3 + H 2 –Pt/Pd  CH 3 CHOH(CH 2 ) 3 CH 3

Practice Reduce Pentanal (str,cond, name prod) Reduce Pentanal (str,cond, name prod)

The 2 nd Reaction Type 2. Oxidation of aldehydes to carboxylic acids O *Carboxyl group: COOH -C-OH O O O O R-C-H –KMnO 4  R-C-OH RCHO –KMnO 4  RCOOH

Examples Oxidize ethanol Oxidize ethanol O O O O C-C-H –KMnO 4  C-C-OH ethanoic acid CH 3 CHO –KMnO 4  CH 3 CO 2 H *To name a carboxylic acid (must be on the 1 st C), drop –e from alkane and add –oic acid

Examples Synthanize pentanoic acid (cond) Synthanize pentanoic acid (cond) CH 3 (CH 2 ) 3 CH 3 + Cl 2  CH 3 (CH 2 ) 3 CH 2 Cl + HCl CH 3 (CH 2 ) 3 CH 2 Cl + H 2 O  CH 3 (CH 2 ) 3 CH 2 OH + HCl CH 3 (CH 2 ) 3 CH 2 OH –PCC/CH 2 Cl 2  CH 3 (CH 2 ) 3 CHO + H 2 CH 3 (CH 2 ) 3 CHO –KMnO 4  CH 3 (CH 2 ) 3 CO 2 H

3 RD Reaction Type Rxn with alcohols to form hemiacetals and acetals Rxn with alcohols to form hemiacetals and acetals *Works well with aldehydes but difficule with ketones

Example with Ketone O H+ OH H+ OR’ O H+ OH H+ OR’ R-C-R + R’OH  R-C-R + R’OH  R-C-R +H 2 O OR’ OR’ OR’ OR’ hemiacetal acetal hemiacetal acetal RCOR + R’OH –H+  RCOR’(OH) + R’OH –H+  RC(OR’) 2 R + H 2 O

Example with Aldehyde O H+ OH H+ OR’ O H+ OH H+ OR’ R-C-H + R’OH  R-C-H + R’OH  R-C-H +H 2 O OR’ OR’ OR’ OR’ RCHO + R’OH –H+  RCHOR’(OH) + R’OH –H+  RCH(OR’) 2 + H 2 O

Practice Example React butanal w/ propanol (str, cond) O OH OH OH O OH OH OH C-C-C-C-H + C-C-C –H+  C-C-C-C-H + C-C-C O-C-C-C O-C-C-C -H+  C-C-C-C-H + H 2 O-C-C-C O-C-C-C

Practice Example Condensed version of the previous example Condensed version of the previous example CH 3 (CH 2 ) 2 CHO + CH 3 CH 2 CH 2 OH –H+  CH 3 (CH 2 ) 2 CH(O(CH 2 ) 2 CH 3 )(OH) + CH 3 CH 2 CH 2 OH –H+  CH 3 (CH 2 ) 2 CH(O(CH 2 ) 2 CH 3 ) 2 + H 2

Practice React 2-pentanone with ethanol (str, cond) React 2-pentanone with ethanol (str, cond)