Citral

The mono terpenoid citral which is found in lemon, orange and lemon grass etc

1. citral Presented by kiran khan

2. Serial no Topics Slide no 1 Definition of citral 3,4 2 Physical properties of citral 5 3 Isoprene units of citral 6 4 Occurrence of citral 7,8,9,10 5 Isolation of citral 11,12 6 Industrial synthesis of citral 13,14 7 Reactions of citral 15,16,17,18,19 8 Structure elucidation of citral 20,21,22,23,24,25,26 9 Uses of citral 27  

3. Definition Citral, or 3,7-dimethyl-2,6 octadienal  or  lemonal , is either a pair, or a mixture of  terpenoids  with the molecular formula C10H16O. The two compounds are double bond isomers. The E-isomer is known as geranial or citral A. The Z-isomer is known as  neral  or citral B. Due to cis–trans isomerism at the C=C bond nearly the aldehyde group obtained from essentials oils of plant sources.

4. Definition The isomer geranal has strong lemon odour . The isomer neral has lemon odour is less strong and sweeter. Geranal Neral

5. Physical properties of citral Citral is a clear yellow colored liquid with a lemon-like odor. Less dense than water and insoluble in water Melting point of citral is <-10°C Density of citral is 0.9 g/cm³ Citral is not stable to alkanes and strong acid When heated to decomposition it emits acrid smoke and irritating fumes

6. Isoprene units of citral Citral is an α,β-unsaturated aldehyde classified as a  monoterpenoid  compound from the 3,6-dimethyloctane series, characterized by a head-to-tail linkage of two isoprenoid subunits

7. Occurance Citral is present in the oils of several plants including  lemon myrtle  cultivated in Australia for  flavouring  and essential oil. It is the highest natural source of citral . Citral as an isolate in steam distilled lemon myrtle oil is typically 90–98%,

8. Occurrance Lemon grass It is cultivated in India, south east Asia and Africa Lemon grass is a good source of lemon grass oil which is a good source of natural citral Lemon grass oil contain 85-65%

9. Occurrence  lemon tea-tree   It is grown in plantations in Kenya, South Africa, and Australia. The essential oil of tea tree contain 70-80% citral .

10. Occurrence Lemon balm The lemon balm contain 11% citral It is cultivated in  to south-central Europe, North Africa, the Mediterranean region, and Central Asia

11. Isolation of citral Citral is 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 seprated now the thus obtained is the lemon grass oil which contain 85%

12. Industrial synthesis of citral First part clasien rearrangement Involves and oxygen in a chair like transition state Second part cope rearrangement Only carbon is involved in a chair like transition state These two reactions happen in succession when the two starting materials are heated together, and the reaction is driven by formation of conjugated carbonyl group in the product

13. Reactions of citral Reduction of citral Citral is reduced to either citranellal or nerol /geraniol The H2 catalyst either reduce the double bond or it will reduce the aldehyde to alcohol

14. Reactions of citral Synthesis of ionone from citral in which an aldol condensation reaction followed by the rearrangement reaction First step is the nucleophillic addition of carbanion of acetone on carbonyl carbon of citral is the base catalyzed reaction The aldol condensation product eliminate water through enolate ion

15. Reaction of citral Step 2 the reaction is proceed by acid catalysis where a double bond opens to from the carbocation A rearrangement reaction followed by ring closure then the proton is abstracted from the molecule by proton acceptor Y to form ionone

16. Structure elucidation of cital Citral form both mono and di bisulfite by the addition of sodium bisulfite to reveal the presence of conjugated aldehyde group its UV spectrum displayed a band at 238 nm to confirm this.

17. Structure elucidation of citral Mass spectrum Molecular mass of citral is 152 Citral show a peak at m/z 29 due to hemolytic alpha cleavage It shows a peak at m/z 69 due to beta cleavage It shows a peak at m/z 124 due heterolytic alpha cleavage

18. Mass spectrum of citral 69

19. Structure elucidation of citral IR spectrum CH stretch for alkanes 3000-2850 CH3 bending 1450 and 1375 CH2 bending 1465 C=C 1680-1600 C=O 1740-1720

20. Infrared spectrum of citral CH stretch CH3 CH2 bend C=O C=C

21. Structure elucidation of citral C-13 NMR The chemical shift of C1 185 to 220 ppm The chemical shift of C2 and C3, C7 and C8 100 to 150 ppm The chemical shift of C4, C9, C10 8-30 ppm The chemical shift of C5 and C6 15 to 55 ppm 1 2 3 4 5 6 10 7 9 8

22. Structure elucidation of citral Proton NMR Proton at C1 has chemical shift value 9.4-9.8 ppm No of protons at C2 and C3 has chemical shift value 5.0-6.0 ppm No of protons at C5 and C4 has chemical shift value 1.9 ppm No of protons at C6, C7 and C8 has chemical shift value 1.7ppm 1 2 3 4 5 6 7 8

23. Uses of citral Citral is an aroma compound used in perfumery for its citrus effect Citral is used as a flavor and for fortifying lemon oil Citral has strong antimicrobial qualities Citral is used in the synthesis of Vitamin A. ionone and methylionone , Mask the smell of smoke

24. Reference https://en.wikipedia.org/wiki/Citral http://www.omicsonline.org/open-access/synthesis-of-citral-acetals-from-lemon-grass-oil-jaa.1000091.php?aid=24074 http://www.chemicalbook.com/ChemicalProductProperty_EN_CB8364074.htm http://onlinelibrary.wiley.com/doi/10.1002/hlca.19760590642/pdf http://www.revolvy.com/main/index.php?s=Citral&uid=0&gowriteups=1&cmd=all http://www.process-nmr.com/citronella_essential_oil.htm https://pubchem.ncbi.nlm.nih.gov/compound/Citral#section=Stability