This document summarizes information about various aldehydes and ketones found in plants. It discusses acyclic, alicyclic, and aromatic aldehydes including citronellal, citral, perillaldehyde, benzaldehyde, and vanillin. It also covers monocyclic, bicyclic, and degraded terpene ketones such as carvone, menthone, fenchone, camphor, and ionones. The document provides details on the occurrence, isolation, identification, properties, synthesis and uses of these compounds. It is a comprehensive overview of important phytochemicals within the classes of aldehydes and ketones.

1. Phytochemistry
Volatile oils
Aldehydes & Ketones
By
Dr. Mostafa Mahmoud Hegazy ( PH.D.)

2. Aldehydes
Terpene
aldehydes
Aromatic
aldehydes
Heterocyclic
aldehydes
Aliphatic
or Acyclic
Alicyclic

3. Common reactions of
aldehydes and
ketones(Derivatization):
• to facilitate their isolation, identification,
and estimation

4. 1- Reaction with sodium bisulfite:
C O NaHSO3 C
OH
SO3Na
C
OH
SO3 Na++
-
or
dilute acid or
Na2CO3/ heatSodium bisulfite Bisulfite derivative
2- Reaction with neutral sodium sulfite:
C O Na2SO3 H2O C
OH
SO3Na
+ + + NaOH
Sodium sulfite dilute acid or
Na2CO3/ heat
3- Reaction with semicarbazide:
C O
N
H
H2N
O
NH2 N
H
N
O
NH2
C H2O+
semicarbazide semicarbazone
+
Addition or adsorption reactions

5. Hydroxylamine HCl Method
RCHO NH2OH.HCl R-CH
Oxime
Phenyl hydrazine Method
RCHO
Hydrazone
Condensation reactions
NOH H2O HCl
C6H5-NH-NH2 RCH3 =N-NH-C6H5 H2O

6. Acyclic terpene aldehydes
Citronellal
terpinolene form limonene form
• It occurs in oil of Citronella, Eucalyptus, Lemon
• Can be obtained by reduction of citral
CHO CHO
Citronellal

7. • Isolation: through its crystalline
bisulphite compound, the aldehyde can be
regenerated by treating the normal bisulphite with
dil. Alkalies (Sodium bicarbonate), strong alkali
hydroxides cause resinification
CHO
SO3Na
SO3Na
OH
SO3Na
OH
SO3Na

8. Separation of citronellal from citral:
citral more reactive than citronellal…… why?
1- neutral sulfite method: With dilute soluton of sod.
Sulphite/ sod. bicarb. mix., in which citral reacts only
(citronellal reacts with conc. solution with passing CO2
at first)
2- bisulfite method:
• With dil. sod. bisulphite citral reacts giving
normal bisulphite which can be regenerated,
while citronellal reacts only with coc. sol.

9. Uses:
• Citronellal used in perfumes industry and
for scenting of soaps.
• It may serves in artificial citrus flavors.
• insect repellent

10. Citral
•Mixture of at least 4 geometrical isomers of di-olefinic
aldehyde
•In oil of lemon grass, Cymbopogon spp.
•Lemon-like odor, yellowish, optically inactive
CHO
CHOCHO
CHO
H H
H H
Geranial (Citral a) Neral (Citral b)

11. Citral
Crystalline product
NaOH
The oil of lemon grass
shaking with
sodium bisulfite
1) washed with alcohol or ether
2)
Isolation

12. CHO
H
(Citral)Geraniol
Synthesis
CH2OH
H
oxidation oxidation
Linalol
OH

13. Separation of Citral a and b
Mixture of Citral a and b + NaHSO3 sodium
bisulfite derivative of Citral a is sparingly soluble while that of
Cital b is readily soluble.

14. Properties
•It is slightly yellowish optically inactive,
possessing a powerful lemon-like odor and
flavor.
•Upon hydrogenation with Na/Hg/H+
→
geraniol or citronellal and citronellol.
Identification: through semicarbazone derivative

15. Uses
• Compounding of synthetic lemon, lime and orange
flavor
• Scenting soaps, cosmetics, perfumes
• Synthesis of ionone: the starting material for synthesis
of vitamin A
CHO
H
condensation
CH3H3C
O
H
O
CYCLIZATION
O O
α-ionone β-ionone
pseudo ionone
Citral
- H2O

16. Cyclic Aldehydes
• Cuminaldehyde
• Perillaldehyde
• Phellandral
• Safranal
• Myrtenal

17. Perillaldehyde
• Oil of Perilla (Labiatae)
• Give oxime with hydroxylamine called
perillatrine or prilla sugar which is 200
time as sweet as sucrose and used as
sweetening agent in Japan

18. Aromatic aldehydes
(Benzaldehyde(
• In bitter almond in glycosidic form “Amygdalin”
• Colorless with bitter almond odor found also in peach and apricot
kernels
• In air, it oxidizes to benzoic acid which can be prevented by
adding 10% alcohol
• Isolated by formation of sod. bisulfite adduct and the aldehyde
can be regenerated by alkali
CH
H2O
CHO 2Glucose
+
+
Amygdalin
(non-volatile)
Benzaldehyde
(Volatile)
H2O
emulsin
O gentiobiose
CN
HCN
(Volatile)
+

19. laetrile semisynthetic
derivative
introduced under name vit B17

20. • Separation of benzaldehyde
from HCN:
By shaken with calcium hydroxide and
ferrous sulphat, stay for a long time to
fix HCN as calcium ferrocyanide,then distilling
benzaldehyde

21. Synthesis
1- By oxidation of benzyle alcohol
2- Oxidation of toluene with manganese
oxide or chromyl chloride
3- Hydrolysis of benzoyl chloride using
ferric benzoate or powdered iron as a
catalyst

22. Vanillin
• In vanilla pods in the form of glucovanillin
CHO
O-glc
OCH3
H2O
CHO
OH
OCH3
Glucose+ +
Glucovanillin
(non-volatile)
Vanillin
(Volatile)
H2O
β-glucosidase
Prepared by:
•Hydrolysis of Vanilla pods powder then extraction with ether;
after evaporating ether, vanillin is crystallized from alcohol

23. Synthesis
1- From eugenol
OH
OCH3
OH
OCH3
OAc
OCH3
CHO
OAc
OCH3
CHO
OH
OCH3
KOH HClAcetylation Oxid.
Heat
Eugenol Isoeugenol
Vanillin

24. 2-From oxidation of lignin waste

25. 3- Reimer-Tiemann's reaction
Industrially from guaiacol, by treatment with
chloroform and sodium hydroxide, both
vanillin and O-vanillin are formed

26. Vanillin as Phenolic Aldehyde
• Vanillin possesses both characters of
aldehydes and phenols, thus acidic to litmus
and give blue color with ferric chloride

27. • Uses
• It used mostly for the
flavoring of food, candies,
and chocolate.
• It serves in perfumes and
cosmetics for imparting
odor.

28. Ketones
Acyclic ketones Alicyclic ketones Aromatic ketones
Monocyclic Bicyclic
e.g.
Menthone
Carvone
Diosphenol
e.g.
Fenchone
Camphor

29. Monocyclic Terpene Ketones
O
(-)-Carvone
•
Occurrence:
•d-form in oil of Caraway
•l-form in oil of Mentha spicata
•dl-forms in oil of Ginger grass

30. Isolation
Oil + aq. Na2SO3 solution
- Neutalization of the liberated
NaOH with dil. acid
-
ether layer
Non reacting compounds
Hydrosulfonic acid salt
Carvone
NaOH
Shake with ether

31. Isolation
The alcoholic solution of oil + NH3
- H2S gas
Carvone
alkali
Carvone hydrogen sulphide complex
O
SO3Na
OH
O
SO3Na
H
. H2S 2 NaOH
Carvone Carvone
disulphonic
acid sodium salt
Carvone
hydrogen sulphide
complex
+ H2S / NH3 + 2 Na2SO3.H2O
+

32. Properties
•Colorless liquid, with caraway odor.
O
Carvone
(Ketone)
• H2SO4
or
H3PO4
or
ZnCl2
OH
Carvacrol
(Phenol)
Uses
Carminative, flavoring, gargles, toothpaste
and substitute for caraway oil.

33. Monocyclic Terpene Ketones
Diosphenol
O
OH
Diosphenol
It is known also as “Buchu camphor”.
Occurrence:
•It occurs in oil of Buchu leaves.
Isolation:
1-rich oil repeatedly cooled to – 20 °C separated
as crystals.
2-for oil with moderate amounts By fractional
distillation in vacuum, collecting the fraction distilling at
109-110°C;
•3-extraction with alkali …acidifiction. and ext. with ether..Being enolic
OH (phenolic properties), it can form water-soluble salt with alkali

34. Properties:
Diosphenol is a crystalline, colorless, sublimable
substance with a camphor-like odor.
Identification:
•It reduces Fehling’s solution and ammoniacal AgNO3
solution.
•It gives intense green color with FeCl3.
Uses: Antiseptic

35. Menthone
• Occurs as a mixture of d-, l-,
and dl- of menthone and
isomenthone.
• Heating of l-menthone with acid
or alkali gives d-isomenthone.
• l-menthone occurs in oils of
Peppermint, Buchu.
• Ment-like odor.
O
Menthone
H

36. Isolation
• Menthone does not react easily with
bisulphite, therefore, it can be isolated
through its oxime or semicarbazone
derivatives, menthone can be
regenerated with dilute acid.
• Uses:
Ingredient in compounding artificial
essential oils.

37. Bicyclic terpene ketones
Occurrence
The d-Fenchone occurs in Fennel oil,
while Thuja oil contains the l-form.
Isolation:
1-The fraction boils between
190-195 °C is rich in fenchone.
O
Fenchone

38. 2(By gentle warming with conc. HNO3,
)Fenchone is stable, Not oxidizing with HNO3, other
constituents are oxidized(.
3-extraction with organic solvent then cooling for
crystalization
Uses:
It is used as a flavoring agent in foods and perfumes
and as a counter irritant.
antiseptic and antispasmodic )it passes kidney stones(

39. Bicyclic terpene ketones Camphor
• d-camphor in camphor tree
)Cinnamomum camphora(,
sassafras, lavander, rosemary
• l and dl present in Lavander,
Salvia
• Crystalline and sublimable
• Identified by semicarbazone derivatives
O
(+)-Camphor

40. Preparation
• Isolation:
• from camphor tree by steam distillation …. then purification with
mix. of charcoal and soda lime….. then sublimation
• Cooling or freezing the oil )high %(
• Fractional distillation then cooling )low %(
• Formation of insoluble complex with strong acids e.g. 80% H2SO4
• Synthesis: From alpha-pinene

41. HO
Cl
Cl
HCl gas
- 10 o
C
isomerization KOH
(+)-α-Pinene Pinene HCl Bornyl chloride
(white ppt.)
Borneol
(pinnane to camphane)
O
Camphor
HNO3
Oxid.
α-pinene therefore used for preparation of synthetic Camphor
molecular
rearrangment
Property Natural camphor Synthetic camphor
Optical Rotation Optically active )d or l( Optically inactive )dl(
Test for Chlorides Negative Positive
Vanillin /HCl and
careful heating
Yellow to green to blue color
)due to other volatile
contaminants(
Yellow

42. Chemical properties
O
NaHSO3
NO adduct
Na/ neutral solvent
reduction
HO HO
Borneol
main
IsoborneolPt
hydrogenation
Isoborneol
main
Camphor
HO

43. •Separation of camphor from borneol
1( Borneol with phthalic or succinic anhydride,
add NaOH → borneol acid phthalate or
succinate ) sol. in aq. alk. layer(. Camphor is
separated by extraction with organic solvent e.g.
ether or by distillation.
2( Camphor can be converted to its oxime, the
oxime is then dissolved in H2SO4, borneol
removed by extraction with ether

44. Uses
Excellent plasticizer for cellulose esters and ethers; used in manufacture of
plastics especially celluloid.
It is used in manufacture of varnishes and explosives, as a moth repellent
and preservative in pharmaceuticals and cosmetics.
Camphor is an ingredient of camphorated parachlorophenol and paregoric.
It is applied as a topical anti-infective and counter irritant.
Camphor derivatives of pharmaceutical importance:
Bromo d-Camphor is powerful counter irritant.
d-Camphor carboxylic acid was used as its basic bismuth sodium salt as
antisyphilitic.
Camphotamide, prepared by condensation of camphor sulphonic acid with
nikethamide, is used as analeptic.

45. Ketones arising from terpene degradation
Ionones O
β-Ionone
O
α-Ionone
C-13 isoprenoids that arise
from the autoxidation of carotenes
Irones
O
β-Irone
C-14 ketones

46. For more educational lectures
cognosy4all.blogspot.com

47. cognosy4all.blogspot.com
Pharmacognosy and Herbal Medicine Dr. Mostafa