Organic chemistry for medicine and biology students Organic B Chapter 18 Aldehydes and Ketones
Organic Chemistry Aldehydes and Ketones Chapter 17.
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Transcript of Organic Chemistry Aldehydes and Ketones Chapter 17.
![Page 1: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/1.jpg)
Organic Chemistry
Aldehydes and Ketones
Chapter 17
![Page 2: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/2.jpg)
Aldehydes and Ketones
Carbonyl Group C=O Present in aldehydes and ketonesC
O
H
C
O
HR C
O
HR C
O
R'R C
O
R'R
Aldehydes Ketones
![Page 3: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/3.jpg)
Aldehydes
Aldehydes Sometimes abbreviated RCHO Contain at least one H connected to the C
C
O
HR C
O
HR
Aldehydesbenzaldehyde
C
O
H
benzaldehyde
C
O
H
acetaldehyde
CHCH3
O
acetaldehyde
CHCH3
Oformaldehyde
H2C O
formaldehyde
H2C O
![Page 4: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/4.jpg)
Ketones
Ketones Carbonyl C is connected to two alkyl groups RCOR’
C
O
R'R C
O
R'R
Ketones
acetoneCH3CCH3
O
acetoneCH3CCH3
O
methyl ethyl ketone
C OCH2CH3
CH3
methyl ethyl ketone
C OCH2CH3
CH3
![Page 5: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/5.jpg)
Nomenclature
IUPAC– Suffix is “-al” for the aldehydes– Suffix is “-one” for the ketones– # indicates position of ketone
propanalCHCH2CH3
O
propanalCHCH2CH3
O
3-hexanone
CH3CH2CCH2CH2CH3
O
3-hexanone
CH3CH2CCH2CH2CH3
O
![Page 6: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/6.jpg)
Nomenclature
NOTE:
Ketone,
Not keytone
From Yahoo Images
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1-chloro-4-penten-2-oneCH2CCH2CHH2C
O
Cl1-chloro-4-penten-2-one
CH2CCH2CHH2C
O
Cl
Nomenclature
An Aldehyde or Ketone takes precedence over any previously considered group
5-chloro-4-hydroxypentanal
CHCH2CH2CHCH2
OOH
Cl5-chloro-4-hydroxypentanal
CHCH2CH2CHCH2
OOH
Cl
![Page 8: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/8.jpg)
Nomenclature
Common names - aldehydes
benzaldehyde
C
O
H
benzaldehyde
C
O
H
acetaldehyde
CHCH3
O
acetaldehyde
CHCH3
Oformaldehyde
H2C O
formaldehyde
H2C O
![Page 9: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/9.jpg)
Nomenclature
Common names - ketones– Some are always used
acetoneCH3CCH3
O
acetoneCH3CCH3
O
methyl ethyl ketone
C OCH2CH3
CH3
methyl ethyl ketone
C OCH2CH3
CH3
benzophenone
CO
benzophenone
CO
- Others name each R group and end with “ketone”
methyl t-butyl ketone
C
O
C
CH3
CH3
CH3
CH3
methyl t-butyl ketone
C
O
C
CH3
CH3
CH3
CH3
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
![Page 10: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/10.jpg)
Physical PropertiesCarbonyls: 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
C O
![Page 11: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/11.jpg)
Physical Properties
Aldehydes and Ketones
– can form H bonds with water!
– solubility in water is about the same as alcohols
C O
C O
C O
H OH
yes!
![Page 12: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/12.jpg)
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
![Page 13: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/13.jpg)
How do you make Aldehydes?
Aldehydes from Oxidation of 1o alcohols– Problem is over oxidation to ACID!
CH2CH3 OH
ethanol
+ K2Cr2O7H+
acetaldehyde
CHCH3
O
acetaldehyde
CHCH3
O
+ K2Cr2O7H+
acetic acid
CCH3 OH
O
CH2CH3 OH
ethanol
+ K2Cr2O7H+
acetaldehyde
CHCH3
O
acetaldehyde
CHCH3
O
+ K2Cr2O7H+
acetic acid
CCH3 OH
O
Practice a couple …………..
![Page 14: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/14.jpg)
How do you make Ketones?
Ketones from Oxidation of 2o alcohols
CH3CHCH3
OH
2-propanol
+ K2Cr2O7H+
acetone
CH3CCH3
O
acetone
CH3CCH3
O
+ K2Cr2O7H+
N.R.
CH3CHCH3
OH
2-propanol
+ K2Cr2O7H+
acetone
CH3CCH3
O
acetone
CH3CCH3
O
+ K2Cr2O7H+
N.R.
Practice a couple …………..
![Page 15: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/15.jpg)
Oxidation of Aldehydes
Aldehydes are easily oxidized– KMnO4
– K2Cr2O7
– even air oxidation carboxylic acid!
+ KMnO4
acetaldehyde
CHCH3
O
acetic acid
CCH3 OH
O
+ KMnO4
acetaldehyde
CHCH3
O
acetic acid
CCH3 OH
O
![Page 16: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/16.jpg)
Oxidation of Ketones Ketones resist oxidation:
– under mild or normal conditions, no reaction– more severe conditions yield mixtures
– CO2 and H2O under extreme conditions
CH3CCH3
O
acetone
normalconditions
N.R.CH3CCH3
O
acetone
normalconditions
N.R.[O]
This difference in reactivity can be used to Tell the difference between an aldehyde and ketone
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Reaction
1. Oxidation – Tollens Test
- Benedicts Test
2. Reduction – Hydrogen addition
– NaBH4 reagent
3. Addition of Alcohols – hemiacetal/acetal
and tautomerism
![Page 19: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/19.jpg)
Tollen’s Test
The Silver Mirror Test Oxidation of Aldehydes
Ag+ ion in aq. ammonia NO reaction with KETONES
Ag(NH3)2+ + aldehyde Silver Mirror
Ag+ + 2 NH3 Ag(NH3)2+
Ag(NH3)2+ + RCHO Ago + RCOO- + 4NH3
![Page 20: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/20.jpg)
Benedict’s Test
Oxidation of Aldehydes Cu++ ion, aqueous Orange to red ppt. NO reaction with KETONES
Cu++ + aldehyde Cu+(oxide) + acid
Cu+Cu2+
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Benedict’s Test
Oxidation of Aldehydes overall reaction
C
O
HRaldehyde
+ 2 Cu2+ + 5 OH -
C
O
O-Rcarboxylic acid (ion)
+ 2 Cu2O + 3 H2O
C
O
HRaldehyde
+ 2 Cu2+ + 5 OH -
C
O
O-Rcarboxylic acid (ion)
+ 2 Cu2O + 3 H2O
Cu2O
![Page 22: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/22.jpg)
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
C
O
+
-
![Page 23: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/23.jpg)
Addition of H2
Reduction to Alcohols– Hydrogen gas and a catalyst (Ni, Pd, Pt)– Similar to alkene to alkane reduction
acetaldehyde
CHCH3
OH2
catalystethanol
CH2CH3
OH
acetaldehyde
CHCH3
OH2
catalystethanol
CH2CH3
OH
![Page 24: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/24.jpg)
Addition of H2
Reduction to Alcohols– Will reduce ketones to 2o alcohols– Slower reaction than reduction of C=C
» C=C is reduced faster (first) if both C=O and C=C
acetoneCH3CCH3
OH2
PtCHCH3
OH
CH3
2-propanolacetone
CH3CCH3
OH2
PtCHCH3
OH
CH3
2-propanol
2-butenalCHCHCHCH3
OH2
Ni butanaldehyde
CHCH2CH2CH3
O
2-butenalCHCHCHCH3
OH2
Ni butanaldehyde
CHCH2CH2CH3
O
![Page 25: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/25.jpg)
Addition of H2 using NaBH4
Reduction to Alcohols– NaBH4 does not allow the reaction of the carbon
carbon double bond
OH
O
OH
NaBH4
H2O
![Page 26: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/26.jpg)
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
acetaldehydeCHCH3
O
+ethanol
CH2CH3 OH CCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
acetaldehydeCHCH3
O
+ethanol
CH2CH3 OH CCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
![Page 27: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/27.jpg)
Formation of Acetals
IF strong acid (HCl) is present, a second alcohol reacts to form the acetal (two -OR groups on C)
CCH3 H
OCH2CH3
OCH2CH3
acetal
H+
CH2CH3 OHCCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
CCH3 H
OCH2CH3
OCH2CH3
acetal
H+
CH2CH3 OHCCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
+ H2O
![Page 28: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/28.jpg)
Addition of Alcohol - Acetals
acetaldehydeCHCH3
O
+ethanol
CH2CH3 OH CCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
CCH3 H
OCH2CH3
OCH2CH3
acetal
H+
CH2CH3 OHCCH3 H
OH
OCH2CH3
hemiacetal(not isolated)
Step 1
Step 2
+ H2O
![Page 29: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/29.jpg)
Formation of Acetals
Addition of R-OH– acid catalyzed, 2 moles of alcohol react
butyraldehyde + isopropyl alcohol
CH3CHCH3
OH
CHCH2CH2CH3
OH+
?
![Page 30: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/30.jpg)
Formation of Acetals
Addition of R-OH– acid catalyzed, 2 moles of alcohol react
butyraldehyde + isopropyl alcohol
CH3CHCH3
OH
CHCH2CH2CH3
OH+
CHCH2CH2CH3
O
CH
OCH
H3C CH3
H3C CH3
acetal
Draw the Hemi
![Page 31: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/31.jpg)
Formation of Acetals
Acetal reaction in equilibrium
CHCH2CH2CH3
O
CH
OCH
H3C CH3
H3C CH3
+ 2 H2OH+
CHCH2CH2CH3
O
CH3CHCH3
OH
+ 2CHCH2CH2CH3
O
CH
OCH
H3C CH3
H3C CH3
+ 2 H2OH+
CHCH2CH2CH3
O
CH3CHCH3
OH
+ 2
![Page 32: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/32.jpg)
Formation of Acetals
Acetal reactions
CH2CH2 C H
O +
ethanol
CH2CH3 OHH+
?
![Page 33: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/33.jpg)
Formation of Acetals
Acetal reactions
?CH2 OH
+CHCH3
OH+
![Page 34: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/34.jpg)
Formation of Acetals
Hemiacetal reactions (formation of hemiacetals)
– likely when within the same molecule
CHCH2CH2CH2CH2
OOHor
HO O O OH
a cyclic hemiacetal
11
2
2
3
3
45 5
4
![Page 35: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/35.jpg)
Formation of Acetals
Cyclic hemiacetals– Reacts with a 2nd. molecule of alcohol– Results in a cyclic acetal
O OH
a cyclic hemiacetal
+ R'-OHH+ O OR'
a cyclic acetal
![Page 36: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/36.jpg)
Formation of Acetals
Which are hemiacetals / acetals?
OCH3CH2 CH2CH2 OH
CHCH3 OH
CH3O
CH3CCH2CH2CH3
CH2 CH3O
CH3O
OHOCH3
OH
OCH3
O
OH
O
OCH3OCH3CH2 CH2 OH
CH3CCH3
OH
CH3OCH3CHCHCH2CH2CH3
OH CH2 CH3O
1 2 3
4 5 6
7 8 9 10
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
![Page 37: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/37.jpg)
Keto-Enol Tautomerism
Equilibrium that exists Keto (carbonyl) to Enol (alkene/alcohol)
acetaldehyde
CC
O
HH
H
H
CC HH
H
O H
"enol" form
![Page 38: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/38.jpg)
Keto-Enol Tautomerism
Equilibrium called Tautomerism
acetaldehyde
CC
O
HH
H
H
CC HH
H
O H
"enol" formKeto form
(more stable) (less stable)
![Page 39: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/39.jpg)
Keto-Enol Tautomerism
Equilibrium called Tautomerism
2,4-pentanedione
CH3CCH2CCH3
OO
"enol" form
CH3CCH2CCH3
OOH
(more stable)
Most enols areless stable
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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Important Compounds
Formaldehyde– Gas at RT
– Soluble in H2O
– Formalin» 37% formaldehyde
» found in labs
» preserves by denaturing proteins
– Used to produce polymers
formaldehyde
C OH
H
![Page 41: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/41.jpg)
Important Compounds
Acetaldehyde– bp 21o C– Converted to trimer
» 3 units of acetaldehyde
» called paraldehyde
» once used as a hypnotic/sleep-producer
acetaldehyde
CC O
H
H
H
H
![Page 42: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/42.jpg)
Important Compounds
Acetone– bp 56o C
– Infinitely soluble in H2O
– Excellent industrial solvent:» paints, varnishes, resins
» coatings, nail polish
– Produced in the body» diabetic ketoacidosis
» “acetone breath” acetone
CCC
O
H
H
H
H
H
H
![Page 43: Organic Chemistry Aldehydes and Ketones Chapter 17.](https://reader038.fdocuments.in/reader038/viewer/2022102702/56649ccc5503460f94995391/html5/thumbnails/43.jpg)
Important Compounds
-chloroacetophenone– lachrymators
» tearing of eyes, etc.
– Used as a tear gas– Active ingredient in “Mace”
-chloroacetophenone
CH2C O
Cl