How might you increase the Rf of the starting material? NMR Application to Evalu

Question

How might you increase the Rf of the starting material?

NMR Application to Evaluate the Reduction Product of Curcumin

H2 (g) (xs), 10% Pd/C o 50 90% In this laboratory, you will reduce curcumin (1), the intensely yellow-staining chemical derived from tumeric powder, to tetrahydrocurcumin (2) using the H-cube®'s 10% Pd/C catalyst and hydrogen gas Background: The palladium catalyzed reduction of alkenes, using a 10% Pd on carbon catalyst and hydrogen gas, is an important reaction for hydrogenating double bonds. A large number ofreactions performed in industry, from the search for new pharmaceutical compounds to advanced material synthesis, are catalyzed reductions, and there is a paucity of such reactions in the undergraduate organic laboratory curriculum due to safety concerns with the handling of hydrogen gas in sizable quantities. While there are recent reports of the use of ammonium formate to generate hydrogen gas in situ for PdC catalyzed reductions of chalcones, this laboratory experiment e Thales Nano TME as a demonstration of the convenience, safety, and ease H-cube makes u of of use of a continuous flow reaction system. Curcumin is the primary curcuminoid component of the well-known spice from India, turmeric. While curcumin can be extracted from turmeric in large quantities, other curcuminoids will be present, such as the desmethoxycurcumin (3) and the bis-desmethoxycurcumin (4). Curcumin has been used in Indian medicine since 1900 BC, and it has recently been demonstrated to have several medicinally relevant activities, such as anti-inflammatory, anti-carcinogenic, and anti- viral. While curcumin is suspected to be largely responsible for the useful bioactivity of turmeric, analogs of curcumin such as the tetrahydro-curcumin are also of medicinal interest. HO OH HO OH An interesting characteristic of curcumin (1) is it's bright, canary-yellow color. Hydrogenation of curcumin (1) to tetrahydro-curcumin (2) destroys the conjugation, though keto-enol tautomerism is still present. OH O HOT OH HO OH 1 (Keto-Form) 1 (Enol Form

Explanation / Answer

Thin layer chromatography (TLC)

Increasing the fraction of non polar solvent in mixture of mobile phase i.e. chloroform (95 to 98.5): methanol (5 to 1.5) would show better resolution of Rf values of the curcuminoids (1-4) mentioned in the synthetic procedure.

Double mobile TLC may also improve the resolution (i.e. Rf of curcumin) by using a non polar solvent as first mobile phase followed by drying the plate, then using 98.5 : 1.5 of chloroform: methanol mixture as second mobile phase.

HPLC method

Retention factor in HPLC is also improved by changing the mobile phase

A rapid and sensitive reverse phase high performance liquid chromatography (HPLC) method has been reported (in Journal of Liquid Chromatography & Related Technologies, Volume 36, 2013 - Issue 13) for simultaneous determination of curcumin (1), tetrahydrocurcumin (2) demethoxycurcumin (3), and bisdemethoxycurcumin (4) with resolution >1.5. A mobile phase comprising acetonitrile-methanol-water adjusted to pH 3.0 has been reported to yeild better resolution.

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.