Citral - isolation,identification and structure elucidation

This powerpoint presentation include isolation,identification and structure elucidation of citral by various spectroscopic techniques.

1. GURU GHASIDAS
VISHWAVIDYALAYA,BILASPUR
SESSION-2023
TOPIC-STRUCTURE ELUCIDATION OF CITRAL
GUIDED BY PRESENTED BY
DR.VINODD.RANGARISIR VINAYBISEN
M.PHARM1
ST
SEM
(PHARMACOGNOSY )

2. Contents
INTRODUCTION
OCCURANCE
ISOLATION
IDENTIFICATION AND ANALYSIS-TLC
STRUCTURE ELUCIDATION
-UV
-IR
-MS
-NMR(1H,13C)

3. Introduction
Citral-citralis mainly isolated from lemon grass oil.
Citralis an acyclic monoterpenealdehyde, and being a monoterpene, it is made of two
isoprene units. Citralis a collective term which covers two geometric isomers that have their
own separate names; the E-isomeris named as geranial (trans-citral) or citralA. The Z-
isomeris named neral(cis-citral) or citralB.Thesestreoisomersoccusas a mixture.
Properties –geranial and neralboth are light oily liquid with lemon odour but neralhas an
odour that is not as intense but sweeter than geranial.
Solubilty-citralis practically insoluble in water but miscible with alchol,ether,benzyl
benzoate,glycerol,mineraloil.
geranial
neral
Fig:Lemongrass

4. Occurance
Citralis present in the oils of several plants, including
lemon myrtle(90–98%),
Litseacitrata(90%),
Litseacubeba(70–85%),
lemongrass(65–85%),
lemon tea-tree(70–80%),
Ocimumgratissimum(66.5%),
Linderacitriodora(about 65%),
Calypranthesparriculata(about 62%),
petitgrain(36%),
lemon verbena(30–35%),
lemon ironbark(26%),
lemon balm(11%),
lime(6–9%),
lemon(2–5%), andorange.
Chemical formula C
10
H
16
O
Molar mass 152.24g/mol
appearance Pale yellow liquid
odour Lemon like
density 0.893g/cm
3
Boiling piont 229°C(444°F, 502K )
Vapour pressure 0.22mmHg(20°c)
Properties
Structure of citral

5. Isolation of citral
Citralis isolated from lemon grass oil which is obtained from lemon grass by
steam distillation.
Method–lemon grass (chopped or un chopped) is filled in the distillation flask
and fitted tightly so that the vapours and oils was not leaked out. Now the
steam is injected in to it so that the upcoming steam carries away the essential
oil from the plant material ,then the lemon grass oil as well as the vapours are
passed through the condenser where they condensed as the oil is lighter then
water so it will float through the surface of water and it is then easily separated.
Now the obtained is the lemon grass oil which contain 85% citral.
Purification by fractional crystallization –
To the total oil, first sodium sulphite is added, the citralget converted into its
sulphite salt.
The salt crystallizes out of the solution then crystals are filtered and washed with
ether or chloroform
The product is then subjected to sodium carbonate treatment to recover citral.

6. Identification and Analysis
T.L.C Method
Sample preparation –Dissolved 1mg of citralin1ml of methanol
Stationary phase-Silica gel-G
Mobile phase-pure chloroform
Detecting agent –2-4,dinitrophenyl hydrazine
Procedure-spots are applied over silica gel-G plate→ the TLC plates
are eluted in pure chloroform →the dried plates are sprayed with
2,4-dinitrophenyl hydrazine reagent→citralgives yellow to orange
spots with Rfvalue 0.51.
a)Citralrefrencestandard
b)lemon grass oil sample
Fig-Chromatogram obtained
from a mixture of cisand trans
citral
Cis-0.35
Trans-0.52

7. Structure elucidation of citralby
UV-spectroscopic technique
Presence of -βunsaturationof citral
→ The UV absorption at 238nm indicates the presence of conjugated
aldehyde
→ On treatment with sodium bisulphate (NaHSo
3), citralforms mono as
well as bi sulphite derivative which indicate that one of the double bond
is conjugated with ›C=O group.
→This reaction indicates citralis -βunsaturated aldehyde.
▪citraloxidizes into carboxylic acid without loss of carbon.
→It indicates that carbonyl group is aldehyde.
Fig: UV spectra of neraland
geranial
Ag2O

8. Infrared spectrum of citral
TYPEOF BOND ABSORPTION
FREQUENCY
C-Hstretch for alkanes3000-2850cm
-1
CH3 bending 1450 and 1375
CH2bending 1465
C=C 1680-1600
C=O 1740-1720

9. Mass spectrum of citral
→Molecular mass of citralis 152gm/mol
→Base peak at 69(most stable and abundant)
→citralshows a peak at m/z 69 due to beta
cleavage
→it shows a peak at m/e 29 due to hemolyticalpha
cleavage
→it shows a peak at m/e124 due to heterolyticalpha
cleavage

10. Structure elucidation of citral
(proton NMR spectroscopy)
►Proton at C1 has chemical shift
value 9.4-9.8ppm
►No. Of proton at C2 and C3 has
chemical shift value 5.0-6.0ppm
►No. Of proton at C5 and C4 has
chemical shift value 1.9ppm
►No. Of proton at C6,C7 and C8 has
chemical shift value 1.7ppm

11. C-13 NMR spectroscopy
►The chemical shift of C1 185-
220ppm
►The chemical shift at C2,C3,C7
and C8 100 to 150ppm
►The chemical shift at C4,C9,C10 ,
8-30ppm
►The chemical shift at C5 and C6,
15to 55 ppm

12. Uses
1.Citralis potent biomoleculeand exhibits various important
therapeutic properties like
antimicrobial,antioxidant,anticancer,antidiabeticand anti
inflammatory.
2.Citralis natural additive used in beverages,foodsand
cosmetics.
3.Citralis used in the synthesis of vitamin A,iononeand
methylionone.
4.Mask the smell of smoke