DR ANTHONY MELVIN CRASTO,WorldDrugTracker, helping millions, A 90 % paralysed man in action for you, I am suffering from transverse mylitis and bound to a wheel chair, With death on the horizon, nothing will not stop me except God
DR ANTHONY MELVIN CRASTO Ph.D ( ICT, Mumbai) , INDIA 30 Yrs Exp. in the feld of Organic Chemistry. Serving chemists around the world. Helping them with websites on Chemistry.Millions of hits on google, world acclamation from industry, academia, drug authorities for websites, blogs and educational contributionn

Showing posts with label STRUCTURE ELUCIDATION. Show all posts

Sunday 29 September 2013

ONE LAKH PLUS VIEWS ON ALL MY BLOGS--DR ANTHONY CRASTO

DR ANTHONY MELVIN CRASTO Ph.D

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ANNOUNCING ONE LAKH PLUS VIEWS ON ALL BLOGS- DR ANTHONY CRASTO

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Friday 2 August 2013

COLUMN CHROMATOGRAPHY

A chemist in the 1950s using column chromatography. The Erlenmeyer receptacles are on the floor.

Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms. The main advantage of column chromatography is the relatively low cost and disposability of the stationary phase used in the process. The latter prevents cross-contamination and stationary phase degradation due to recycling.

The classical preparative chromatography column, is a glass tube with a diameter from 5 mm to 50 mm and a height of 5 cm to 1 m with a tap and some kind of a filter (a glass frit or glass wool plug – to prevent the loss of the stationary phase) at the bottom. Two methods are generally used to prepare a column: the dry method, and the wet method.

For the dry method, the column is first filled with dry stationary phase powder, followed by the addition of mobile phase, which is flushed through the column until it is completely wet, and from this point is never allowed to run dry.
For the wet method, a slurry is prepared of the eluent with the stationary phase powder and then carefully poured into the column. Care must be taken to avoid air bubbles. A solution of the organic material is pipetted on top of the stationary phase. This layer is usually topped with a small layer of sand or with cotton or glass wool to protect the shape of the organic layer from the velocity of newly added eluent. Eluent is slowly passed through the column to advance the organic material. Often a spherical eluent reservoir or an eluent-filled and stoppered separating funnel is put on top of the column.

The individual components are retained by the stationary phase differently and separate from each other while they are running at different speeds through the column with the eluent. At the end of the column they elute one at a time. During the entire chromatography process the eluent is collected in a series of fractions. Fractions can be collected automatically by means of fraction collectors. The productivity of chromatography can be increased by running several columns at a time. In this case multi stream collectors are used. The composition of the eluent flow can be monitored and each fraction is analyzed for dissolved compounds, e.g. by analytical chromatography, UV absorption, or fluorescence. Colored compounds (or fluorescent compounds with the aid of an UV lamp) can be seen through the glass wall as moving bands.

Overview

Stationary phase

The stationary phase or adsorbent in column chromatography is a solid. The most common stationary phase for column chromatography is silica gel, followed by alumina. Cellulosepowder has often been used in the past. Also possible are ion exchange chromatography, reversed-phase chromatography(RP), affinity chromatography or expanded bed adsorption(EBA). The stationary phases are usually finely ground powders or gels and/or are microporous for an increased surface, though in EBA a fluidized bed is used. There is an important ratio between the stationary phase weight and the dry weight of the analyte mixture that can be applied onto the column. For silica column chromatography, this ratio lies within 20:1 to 100:1, depending on how close to each other the analyte components are being eluted.

Mobile phase (eluent)

The mobile phase or eluent is either a pure solvent or a mixture of different solvents. It is chosen so that the retention factor value of the compound of interest is roughly around 0.2 - 0.3 in order to minimize the time and the amount of eluent to run the chromatography. The eluent has also been chosen so that the different compounds can be separated effectively. The eluent is optimized in small scale pretests, often using thin layer chromatography (TLC) with the same stationary phase.

There is an optimum flow rate for each particular separation. A faster flow rate of the eluent minimizes the time required to run a column and thereby minimizes diffusion, resulting in a better separation. However, the maximum flow rate is limited because a finite time is required for analyte to equilibrate between stationary phase and mobile phase, see Van Deemter's equation. A simple laboratory column runs by gravity flow. The flow rate of such a column can be increased by extending the fresh eluent filled column above the top of the stationary phase or decreased by the tap controls. Faster flow rates can be achieved by using a pump or by using compressed gas (e.g. air,nitrogen, or argon) to push the solvent through the column (flash column chromatography).

The particle size of the stationary phase is generally finer in flash column chromatography than in gravity column chromatography. For example, one of the most widely used silica gel grades in the former technique is mesh 230 – 400 (40 – 63 µm), while the latter technique typically requires mesh 70 – 230 (63 – 200 µm) silica gel.

A spreadsheet that assists in the successful development of flash columns has been developed. The spreadsheet estimates the retention volume and band volume of analytes, the fraction numbers expected to contain each analyte, and the resolution between adjacent peaks. This information allows users to select optimal parameters for preparative-scale separations before the flash column itself is attempted.

An automated ion chromatography system.

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Typical set up for manual column chromatography

CHECK THIS VIDEO

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CHECK THIS VIDEO

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Monday 29 July 2013

Nickel-Catalyzed Suzuki–Miyaura Couplings in Green Solvents

Stephen D. Ramgren, Liana Hie, Yuxuan Ye, and Neil K. Garg

Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States

Org. Lett., Article ASAP

Publication Date (Web): July 23, 2013 (Letter)

DOI: 10.1021/ol401727y

http://pubs.acs.org/doi/abs/10.1021/ol401727y

The nickel-catalyzed Suzuki–Miyaura coupling of aryl halides and phenol-derived substrates with aryl boronic acids using green solvents, such as 2-Me-THF and tert-amyl alcohol, is reported. This methodology employs the commercially available and air-stable precatalyst, NiCl2(PCy3)2, and gives biaryl products in synthetically useful to excellent yields. Using this protocol, bis(heterocyclic) frameworks can be assembled efficiently.

Friday 26 July 2013

Concise Total Synthesis of a Newly Discovered Alkaloid

A concise synthesis of a novel alkaloid natural product with the pyrroloindoloquinazoline skeleton has been devised
Read more

Tuesday 16 July 2013

A new labdane diterpene from Rauvolfia tetraphylla Linn. (Apocynaceae)

Rauvolfia tetraphylla Linn. (syn. R. canescens L., family: Apocynaceae) holds an important position in the Indian traditional system of medicine, and has other immense applications. This particular plant is regarded as a rich source of a wide variety of important alkaloid constituents such as reserpine, reserpiline, raujemidine, isoreserpiline, deserpidine, aricine, ajmaline, ajmalicine, yohimbines, serpentine, sarpagine, vellosimine and tetrphylline. However, there is no report on the terpenoid constituent from this plant, and we report the isolation from the air-dried stems and branches of R. tetraphylla and structural elucidation of a new labdane diterpene, 3-hydroxy-labda-8(17),13(14)-dien-12(15)-olide (1; Fig. 1) bearing an unusual -lactone moiety.

Fig. 1 Structure of labdane diterpene

Goutam Brahmachari*, Lalan Ch. Mandal, Dilip Gorai, Avijit Mondal, Sajal Sarkar and Sasadhar Majhi

Doi: 10.3184/174751911X13220462651507

read all at

http://www.sciencereviews2000.co.uk/blog/view/journal-of-chemical-research/58/a-new-labdane-diterpene-from-rauvolfia-tetraphylla-linn-apocynaceae/552

Saturday 13 July 2013

Chemistry Living and Systems: 123.101 Lecture 1

allow slideshare to load..............

Chemistry Living and Systems: 123.101 Lecture 1 from Gareth Rowlands

Thursday 4 July 2013

Catalyst duo exerts powerful stereocontrol

The dual catalyst enables selective access to the required stereoisomer © Science/AAAS

Chemists from the Swiss Federal Institute of Technology, ETH Zurich, have teamed chiral catalysts in pairs to selectively drive a reaction towards desired stereoisomeric products with high selectivity. Each catalyst activates one reagent and controls its substituent arrangement as it bonds to the other to form two neighbouring chiral centres. ‘We have shown that it is possible to develop fully stereodivergent reaction processes,’ says Erick Carreira, who led the work. ‘We expect that additional reactions displaying full stereodivergency will be identified.’

read all at
http://www.rsc.org/chemistryworld/2013/05/catalyst-duo-powerful-stereocontrol-diastereomer

References

S Krautwald et al, Science, 2013, DOI: 10.1126/science.1237068

Wednesday 3 July 2013

carboxylic acids

Organic Chemistry Chapter 21 Klein from Sarah Greening

Thursday 27 June 2013

A molecular database for developing organic solar cells

A molecular database for developing organic solar cell

Harvard researchers have released a massive database of more than 2 million molecules that might be useful in the construction of solar cells that rely on organic compounds for construction of organic solar cells for the production of renewable energy. Developed as part of the Materials Genome Initiative launched by the White House’s Office of … more…

http://www.kurzweilai.net/a-molecular-database-for-developing-organic-solar-cells?utm_source=KurzweilAI+Daily+Newsletter&utm_campaign=4fc1bf53a4-UA-946742-1&utm_medium=email&utm_term=0_6de721fb33-4fc1bf53a4-282116853

Monday 24 June 2013

Natural Products from St. John's Wort

Enatiomers (−)-hyperione A and (−)-hyperione B can be synthesised from a common precursor in ten steps
Read more

http://www.chemistryviews.org/details/ezine/1238795/Natural_Products_from_St__Johns_Wort.html

doc b's CV

Wednesday 19 June 2013

Cheap nickel catalysis offers alternative to expensive enzymatic resolution, Switching chirality in amino acids

Amino acids are converted to their opposite enantiomers by complexation with a nickel(II) salt and a chiral ligand Switching chirality in amino acids
	Cheap nickel catalysis offers alternative to expensive enzymatic resolution http://www.rsc.org/chemistryworld/2013/06/switching-chirality-amino-acids-nickel-catalysis

Tuesday 11 June 2013

Bruce Roth Awarded 2013 Perkin Medal

Roth

Credit: Genentech

Bruce Roth Awarded 2013 Perkin Medal

Honors: Chemist was the first to synthesize the cholesterol-lowering drug atorvastatin, also known as Lipitor
The Society of Chemical Industry (SCI) has selected Bruce D. Roth, vice president of discovery chemistry at Genentech, as the winner of the 2013 Perkin Medal. The annual award is recognized as the highest honor given for outstanding work in applied chemistry in the U.S.
http://cen.acs.org/articles/91/web/2013/06/Bruce-Roth-Awarded-2013-Perkin.html

A Molecule Of Many Colors-With rigid wings and a flexible core, a new compound can switch between two shapes and glow one of three colors.

Flexible And Fluorescent

A molecule combining rigid anthraceneimide wings and a flexible cyclooctatetraene core switches between a flat and a bent V shape. The R groups are either hydrogens or n-butyl groups.

Credit: J. Am. Chem. Soc.

A Molecule Of Many Colors

Organic Chemistry: With rigid wings and a flexible core, a new compound can switch between two shapes and glow one of three colors.

A new, flexible, multi-ring organic compound fluoresces red, green, or blue depending on its environment (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja404198h). The molecule’s combination of rigid wings and a flexible center could serve as a general design strategy for molecular sensors, the researchers say.

The molecule, developed by a team of researchers, including Shohei Saito, Stephan Irle, and Shigehiro Yamaguchi of Nagoya University in Japan, has two rigid anthraceneimide wings on opposite sides of a floppy cyclooctatetraene core

read all at
http://cen.acs.org/articles/91/web/2013/06/Molecule-Colors.html

Monday 10 June 2013

ORGANIC CHEMISTRY REACTIONS, website by DR ANTHONY CRASTO

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https://sites.google.com/site/anthonycrastoreactions/home

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Saturday 12 May 2012

Whats new in Chemistry

READ ALL THIS AT
http://amcrasto.biz.ly/whats_new.html

Scientists discover chemistry of passion

http://www.worldofchemicals.com/wocart/7/scientists-discover-chemistry-of-passion.html

Scientists say there is increase in the levels of hormones neutrophins and dopamine when cupid strikes.

LONDON, UNITED KINGDOM: Couples should not worry when the first flush of passion dims - scientists have identified the hormone changes which cause the switch from lust to cuddles. A team from the University of Pisa in Italy found the bodily chemistry which makes people sexually attractive to new partners lasts, at most, two years. When couples move into a “stable relationship” phase, other hormones take over, Chemistry World reports.

LOVE, actually is chemicals racing internally

http://www.worldofchemicals.com/wocart/10/love-actually-is-chemicals-racing-internally.html

Scientists say there is increase in levels of hormones neutrophins and dopamine when cupid strikes.

When couples fall in love, outwardly they experience dizziness, flushed face, sweaty palms and most prominent of all a wildly beating heart. But, internally, the feeling of love is due to chemicals racing around the brain and body.

The feelings, researchers found are due to dopamine, norepinephrine and phenylethylamine that human beings release. Dopamine is thought to be the “pleasure chemical,” producing a feeling of bliss. Norepinephrine is similar to adrenaline and produces the racing heart and excitement. Together these two chemicals produce elation, intense energy, sleeplessness, craving, loss of appetite and focused attention, discovered Helen Fisher, anthropologist at Rutgers University. “The human body releases the cocktail of love rapture only when certain conditions are met. And men more readily produce it than women, because of their more visual nature,” she added.

Wednesday 21 March 2012

Buckminsterfullerene or Buckyball

DEAR VISITOR

http://www.slideshare.net/anthonycrasto64/anthony-crasto-buckyball
------is the link to a presentation on Buckminsterfullerene

File:Buckminsterfullerene.svg

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DR ANTHONY MELVIN CRASTO, helping millions
DR ANTHONY MELVIN CRASTO Ph.D ( ICT, Mumbai) , INDIA 25Yrs Exp. in the feld of Organic Chemistry,Working for GLENMARK GENERICS at Navi Mumbai, INDIA. Serving chemists around the world. Helping them with websites on Chemistry.Million hits on google NO ADVERTISEMENTS , ACADEMIC , NON COMMERCIAL SITE, world acclamation from industry, academia, drug authorities for websites, blogs and educational contribution

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