DEET: Mosquito repellent

There's no doubt about mosquitoes and mosquito bites are annoying. What's worse, mosquito bites sometimes transmit serious diseases, such as West Nile virus, malaria and dengue fever. Mosquito bites are caused only by the bite of a female mosquito. The female mosquito feeds off our blood by piercing our skin with her proboscis. While sucking our blood, she also deposits some of her saliva into the skin. These saliva proteins that remain in our body may react with our body chemicals, resulting in the characteristic itching and bump.

There are many mosquito repellents with different active ingredients sold under different brand names in our markets. Active ingredients approved and commonly used as repellents are DEET (N,N-diethyl-m-toluamide), picaridin and oil of lemon eucalyptus (citriodiol or p-Menthane-3, 8 diol.) etc. Out of these, DEET is the most common active ingredient proven to prevent mosquito bites. DEET was first developed by the United States Army, following its experience of jungle warfare during World War II.

DEET is a registered pesticide. DEET is short for N,N-diethyl-m-toluamide (also known as N,N-diethyl-3-methylbenzamide). It is a member of the toluene chemical family and DEET is slightly yellow liquid at room temperature and can be prepare by converting m-toluic acid to acyl chloride and reacting with diehtylamine.

DEET can be absorbed through the skin and passes into the blood. The Medical Sciences Bulletin, published by Pharmaceutical Information Associates Ltd. reports, "Up to 56% of DEET applied topically penetrates intact human skin and 17% is absorbed into the bloodstream." Blood concentrations of about 3 mg per litre have been reported several hours after DEET repellent was applied to skin in the prescribed fashion. DEET is also absorbed by the gut.

In recent year, huge efforts have been made in the study of mechanism of DEET action. For more detail analysis, experimental data, mode of action and safe dosage, please follow the following links.

Sources:

http://en.wikipedia.org/wiki/DEET

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2518096/

www.npic.orst.edu/factsheets/DEETtech.pdf

http://entomology.ucdavis.edu/news/deet321.pdf

http://www.nyc.gov/html/doh/html/wnv/wnvfaq4.shtml

http://www.epa.gov/opp00001/factsheets/chemicals/deet.htm

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Calixarene-based fluoroionophores as sensor for lead and mercury ions

Birendra Babu Adhikari

The discovery of crown ethers in the 1960s and their unique complexation properties initiated an explosive development in the field that is now called as host-guest chemistry or within a broader sense of understanding as supramolecular chemistry. This gave rise to an enormous number and structural variety of compounds all tracking back to original crown compounds. Apart from parent-type crown compounds, they range over the monocyclic coronands, bi- and oligocyclic cryptands, the spherands, cavitands, carcerands and even more sophisticated structures, all of which opened up new possibilities for cation recognition with improvement of selectivity. Then, the idea of coupling these ionophores to chromophores or fluorophores, leading to so-called chromoionophores and fluoroionophores, respectively, emerged some years later.

 

 

Detecting cations is of great interest to many scientists, including chemists, biologists, clinical biochemists and environmentalists. Fluorescent chemosensors capable of selectively recognizing cations have potential analyzing applications in many diverse areas including chemistry, biology and medicine¹. The heavy metals like mercury and lead are toxic to organisms and early detection in the environment is highly desirable. Selective recognition and separation of heavy metal ions which cause adverse environmental and health problems have been much interest to those concerned with the development of sustainable environment. As a consequence of the rapid development of host-guest chemistry, the supramolecular technology has led to the designing of new fluorescent sensors capable of selectively sensing metal ions. Rewarded as the third generation of supramolecular chemistry, calixarenes with fluorogenic pendant groups have received increasing attention and become promising candidate for the sensing probes because they are in a certain preorganized framework to easily accommodate metal cations and exhibit a selective change in fluorescence emission.

 

Most fluorescent chemosensors for cations consist of a cation recognition unit (ionophore) along with a fluorogenuic unit (fluorophore) and are thus called fluoroionophore. An effective fluorescent chemosensor must convert the event of cation recognition by ionophore into an easily monitored and highly sensitive light signal from the fluorophore¹. Such fluorescence sensors have been designed on the photo-induced mechanism inducing the photophysical changes upon cation binding which include photo induced electron transfer (PET) ^2-7, excimer formation and extinction^8-10 or photo induced charge transfer (PCT) ¹¹. As fluorogenic units, pyrenyl^{2, 3, 8-10}, anthracenyl^{4, 5}, dansyl^{6, 7} etc moieties are appended mainly at lower rim of calixarene platform.

 

 

Lee et al.² developed the pyrene armed calix[4]arene locked in cone conformation having crown-6-loop and amide functional groups as recognition moiety. The compound showed decreasing fluorescence intensity with various metal ions, but especially gave the lead ion selectivity regarding the fluorescence quenching which was ascribed to the reverse PET from pyrene ring to the electron deficient amide oxygen. Kim et al.³ developed the thiacalix[4]crown-based lumino-ionophore with pyrene as fluorogenic moiety which, upon addition of lead metal, showed remarkable fluorescence quenching whereas other transition metals as well as alkali metals and alkaline earth metals had very little fluorescence quenching effect. The results indicated that crown part of calixarene plays an important role in selective binding of lead ion and the fluorescence quenching were described in terms of reverse PET as well as heavy metal effect. Kim et al.⁸ and Kim et al.⁹ independently developed pyrene appended 1, 3-alternate calix[4]arene with two different cation recognition units so that the cation may choose more favorable binding position. One of the compounds was decorated with crwon-5-loop⁸ and another was decorated with carboxyl groups⁹. Both the compounds showed strong excimer emission at around 480 nm. Upon addition of lead ions, fluorescence quenching was observed in both cases which occurred due to conformational change in calixarene upon lead binding. Interestingly, when potassium and calcium ions were added to the lead complex of former and later compounds respectively, the fluorescence was revived due to metal ion exchange process and an interesting ON-OFF switching process was observed. Bok et al.⁴ synthesized Calix[4]crown-based chemosensors with anthracene moiety as fluorophore. The complexation of K⁺ ions caused fluorescence enhancement of the naphthalene unit by chelation enhanced fluorescence (CHEF) whereas Pb²⁺ led to quenching of fluorescence due to PET from anthracenyl moiety to lead ion. Similar quenching behavior upon addition of lead to the fluoroionophore with anthracene group was also observed by Liu et al.⁵ Talanova et al.⁶ developed the fluoroionophore having dansyl group as fluorophore. They observed highly selective ON-OFF type of fluorescence quenching effect upon adding mercury to this compound, which was attributed to electron transfer from excited dansyl moiety to the proximate mercuric ion.

 

In general, many fluorescent based chemosensors for transition metal and heavy metal cations rely on quenching of a fluorescent signal to indicate the complexation by a selective ionophore. More challenging has been the development of chemosensors whose fluorescent intensity is enhanced upon complexation with particular cation. Cha et al.¹² reported a fluorogenic ionophore based on calix[4]arene-azacrown ether having anthracene moiety as fluorogenic group which exhibited pronounced mercury selectivity with enhanced fluorescence in which an important OFF-ON signaling was observed which is the preferential in sensor development.

 

 

To conclude, the unique topology of calixarenes offers a wide range of scaffolds which enables them to encapsulate many different ions provided that they are suitably decorated with proper ligating sites. Some have been studied for the sensing of toxic metal ions. Though many prospects of utilizing calixarenes in cation analysis have been demonstrated, these analyses are largely concerned in organic solvents. Development of highly selective sensing systems for the detection of toxic metal ions, applicable in aqueous media is still one of the major challenges for environmentalists’ analytical chemists’.

References

1. a) B. Valeur, I. Leray, Coord. Chem. Rev. 205 (2000) 3, b) B. S. Creaven, D. F. Donlon, J. McGinley, Coord. Chem. Rev. 253 (2009) 893

2. S. H. Lee, J. Y. Kim, S. K. Kim, J. H. Lee, J. S. Kim, Tetrahedron 60 (2004) 5171

3. S. K. Kim, J. K. Lee, J. M. Lim, J. W. Kim, J. S. Kim Bull. Korean Chem. Soc.25 (2004) 1247

4. J. H. Bok, H. J. Kim, J. W. Lee, S. K. Kim, J. K. Choi, J. Vicens, J. S. Kim Tetrahedron Letters 47 (2006) 1237

5 J.- M. Liu, J.-H. Bu, Q.-Y. Zheng, C.-F. Chen, Z.-T. Huang Tetrahedron Letters 47 (2006) 1905

6. G. G. Talanova, Nazar S. A. Elkarim, V. S. Talanov, R. A. Bartsch, Anal. Chem. 71 (1999) 3106

7. Q.-Y. Chen, C.-F. Chen Tetrahedron Letters 46 (2005) 165

8. S. K. Kim, S. H. Lee, J. Y. Lee, J. Y. Lee, R. A. Bartsch, J. S. Kim J. Am. Chem. Soc. 126 (2004) 16499

9. S. H. Kim, J. K. Choi, S. K. Kim, W. Sim, J. S. Kim, Tetrahedron Letters 47 (2006) 3737

10. J. H. Kim, A.-R. Hwang, S.-K. Chang, Tetrahedron Letters 45 (2004) 7557

11. J. S. Kim, H. J. Kim, H. M. Kim, S. H. Kim,. J. W, Lee, S. K. Kim, B. R. Cho, J. Org. Chem. 71 (2006) 8016

12. N. R. Cha, M. Y. Kim, Y. H. Kim, J.-I. Choe, S.-K. Chang J. Chem. Soc., Perkin Trans. 2, 2002, 1193

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Can Your Kitchen Pass the Food Safety Test?

Information from the next door:….. ……………………..

This post is for general information to all my readers. Talking about our kitchen, that should pass the Food Safety Test and we should be conscious about our eating habit and the place where we prepare and take foods. I have found some general information about the safety of our kitchen and some facts concerning to our health. I hope you will enjoy this post as usual.

What comes to mind when you think of a clean kitchen? Shiny waxed floors? Gleaming stainless steel sinks? Spotless counters and neatly arranged cupboards? They can help, but a truly "clean" kitchen--that is, one that ensures safe food--relies on more than just looks: It also depends on safe food practices.

In the home, food safety concerns revolve around three main functions: food storage, food handling, and cooking. To see how well you're doing in each, take this quiz, and then read on to learn how you can make the meals and snacks from your kitchen the safest possible.

Questions and Answers

Choose the answer that best describes the practice in your household, whether or not you are the primary food handler.

1. The temperature of the refrigerator in my home is:
a. 50 degrees Fahrenheit (10 degrees Celsius)
b. 40 F (5 C)
c. I don't know; I've never measured it.

Refrigerators should stay at 40 F (5 C) or less, so if you chose answer B, give yourself two points. If you didn't, you're not alone. According to Robert Buchanan, Ph.D., senior science adviser and director of science in the Food and Drug Administration's Center for Food Safety and Applied Nutrition, many people overlook the importance of maintaining an appropriate refrigerator temperature.

"According to surveys, in many households, the refrigerator temperature is above 50 degrees (10 C)," he said. His advice: Measure the temperature with a thermometer and, if needed, adjust the refrigerator's temperature control dial.

A temperature of 40 F (5 C) or less is important because it slows the growth of most bacteria. The temperature won't kill the bacteria, but it will keep them from multiplying, and the fewer there are, the less likely you are to get sick.

Freezing at zero F (minus 18 C) or less stops bacterial growth (although it won't kill bacteria already present).

2. The last time we had leftover cooked stew or other food with meat, chicken or fish, the food was:
a. cooled to room temperature, then put in the refrigerator
b. put in the refrigerator immediately after the food was served
c. left at room temperature overnight or longer

Answer B is the best practice; give yourself two points if you picked it.

Hot foods should be refrigerated as soon as possible within two hours after cooking. But don't keep the food if it's been standing out for more than two hours. Don't taste test it, either. Even a small amount of contaminated food can cause illness.

Date leftovers so they can be used within a safe time. Generally, they remain safe when refrigerated for three to five days. If in doubt, throw it out, says FDA microbiologist Kelly Bunning, Ph.D., associate senior science adviser in CFSAN: "It's not worth a food borne illness for the small amount of food usually involved."

3. The last time the kitchen sink drain, disposal and connecting pipe in my home were sanitized was:
a. last night
b. several weeks ago
c. can't remember

If answer A best describes your household's practice, give yourself two points. Give yourself one point if you chose B.

According to John Guzewich, CFSAN's director of emergency coordination and response, the kitchen sink drain, disposal and connecting pipe are often overlooked, but they should be sanitized periodically by pouring down the sink a solution of 1 teaspoon (5 milliliters) of chlorine bleach in 1 quart (about 1 liter) of water or a solution of commercial kitchen cleaning agent made according to product directions. Food particles get trapped in the drain and disposal and, along with the moistness, create an ideal environment for bacterial growth.

4. If a cutting board is used in my home to cut raw meat, poultry or fish and it is going to be used to chop another food, the board is:
a. reused as is
b. wiped with a damp cloth
c. washed with soap and hot water
d. washed with soap and hot water and then sanitized

If answer D best describes your household's practice, give yourself two points.

If you picked A, you're violating an important food safety rule: Never allow raw meat, poultry and fish to come in contact with other foods. Answer B isn't good, either. Improper washing, such as with a damp cloth, will not remove bacteria. And washing only with soap and water may not do the job, either.

To prevent cross-contamination from a cutting board, the FDA advises consumers to follow these practices:

• Use smooth cutting boards made of hard maple or a non-porous material such as plastic and free of cracks and crevices. These kinds of boards can be cleaned easily. Avoid boards made of soft, porous materials.
• Wash cutting boards with hot water, soap, and a scrub brush to remove food particles. Then sanitize the boards by putting them through the automatic dishwasher or rinsing them in a solution of 1 teaspoon (5 milliliters) of chlorine bleach in 1 quart (about 1 liter) of water.
• Always wash and sanitize cutting boards after using them for raw foods and before using them for ready-to-eat foods. Consider using one cutting board only for foods that will be cooked, such as raw fish, and another only for ready-to-eat foods, such as bread, fresh fruit, and cooked fish. Disposable cutting boards are a newer option, and can be found in grocery and discount chain stores.

5. The last time we had hamburgers in my home, I ate mine:
a. rare (140 F)
b. medium (160 F)
c. well-done (170 F)

Give yourself two points if you picked answer B or C.

Ground beef must be cooked to an internal temperature of 160 degrees Fahrenheit (71 degrees Celsius). Using a digital or dial food thermometer is crucial, the U.S. Department of Agriculture says, because research results indicate that some ground meat may prematurely brown before a safe internal temperature has been reached. On the other hand, research findings also show that some ground meat patties cooked to 160 F or above may remain pink inside for a number of reasons; thus the color of meat alone is not considered a reliable indicator of ground beef safety. If eating out, order your ground beef to be cooked well-done. Temperatures for other foods to reach to be safe include:

• beef, lamb and veal--145 F (63 C)
• pork and ground beef--160 F (71 C)
• whole poultry and thighs--180 F (82 C)
• poultry breasts--170 F (77 C)
• ground chicken or ground turkey--165 F (74 C).
  Seafood should be thoroughly cooked to an internal temperature of at least 145 F (63 C). Fish that's ground or flaked, such as a fish cake, should be cooked to at least 155 F (68 C), and stuffed fish to at least 165 F (74 C).

If you don't have a meat thermometer, there are other ways to determine whether seafood is done:

• For fish, slip the point of a sharp knife into the flesh and pull aside. The edges should be opaque and the center slightly translucent with flakes beginning to separate. Let the fish stand three to four minutes to finish cooking.
• For shrimp, lobster and scallops, check color. Shrimp and lobster turn red and the flesh becomes pearly opaque. Scallops turn milky white or opaque and firm.
• For clams, mussels and oysters, watch for the point at which their shells open. Boil three to five minutes longer. Throw out those that stay closed.
  When using the microwave, rotate the dish several times to ensure even cooking. Follow recommended standing times. After the standing time is completed, check the seafood in several spots with a meat thermometer to be sure the product has reached the proper temperature.
  

Sources: http://www.cfsan.fda.gov/~dms/fs-toc.html

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Pyrene: Electrophilic Aromatic Substitution of 7-t-butyl-1, 3-dimethylpyrene:

Pyrene story:

Today I am going to present some typical but simple reactions related to pyrene. I think these reactions opens new access for the further synthesis of polycyclic aromatic hydrocarbons and these compounds might be the reference compounds that can be used for the study of the biological effects of polycyclic aromatic hydrocarbons for the establishment of structure-activity relationships. Analysis of the complicated mixtures of polycyclic aromatic compounds in the environment is possible only when pure and well-characterized reference materials are available.

Electrophilic substitution of pyrene occurs at the 1, 3, 6, and 8 positions, but not at the other position (2, 4,5,7,9 and 10). Therefore, pyrene substituted at the later positions must be prepared in ways other than by direct electrophilic substitution of pyrene itself. Formaylation and acetylating of the pyrene afford selectively 5-mono or 5, 9-disubstituted products depending on the Lewis acid catalyzed used. However; bromination and nitration afford 6-substituted products.

So enjoy the following schemes:

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Flower Chemistry : Hamani in Japan

Flowers of Spring in Japan and Hanami

Spring is fast on its way to Japan and with spring comes a fascination with her flowers. The cherry blossom season is so anticipated that there are even calendars that will tell you when the cherry blossoms will start to bloom.
The best way to celebrate the flowers of spring in Japan is to head out to a local park or garden for a stroll or a picnic - it’s a popular pastime so be prepared for crowds!
Hanami (cherry blossom viewing) has been a Japanese custom since the 7th century when the aristocrats enjoyed looking at beautiful sakura and wrote poems. Sakura is a symbol of Japan, and it's said that there are over four hundred varieties of cherry trees in Japan. The most popular kind of sakura which can be viewed everywhere in Japan is somei-yoshino (Yedoensis). Japanese cherry trees do not yield fruits like other cherry trees.
Hanami and cherry blossom festivals are held all over Japan in spring. In hanami parties, people have fun, drinking, eating, and singing during the day or night. It is like a picnic under sakura trees. Usually, people bring food, do BBQ, or buy food from vendors for hanami parties. Among various food people eat in hanami, dango is the most common. See Japanese food for hanami.
In popular hanami spots, there are even competitions for the best spots. If you do not like a crowd, you can go to mountains or other quiet places for hanami. Stop by any gardens near you. There are sakura trees everywhere in Japan.
Cherry blossoms flower at different times throughout Japan. The cherry blossoms begin blooming in January in Okinawa, and they are at their peak in late March to April in Honshu region. In Hokkaido, cherry blossoms usually become in their peak in May. The blooming period of sakura is very short.

Last year I had some snap shots of sakura flowers. I hope you will enjoy these …

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Aspects of Traditional Medicine in Nepal

Since long we are looking for a huge collection and most scientific book related to Traditional Medicine in Nepal.Its the breakthrough; as recently we have a new book by Prof. M.B. Gewali entitled Aspect of Traditional Medicine in Nepal. This book was edited by Dr. Suresh Awale. Nepal, a small country, stretches from north west to south-east forming an irregular rectangle with 80.4' to 88.12' longitude and 26.22' to 30.27' latitude. In east- west extension it is about 885 km long and north-south extension it varies from 160 to 240 km making total area 147,181 sq. km. It has geographical diversity, which ranges from world's highest region. This has endowed Nepal with great varieties of flora including those of dense tropical monsoon forest of terai, deciduous and coniferous tropical forest, temperate and alpine climatic region. Nepal, a country with extra- ordinary bio-diversity

Major medical systems that are in practice in Nepal are modern Allopathic, Homeopathic, Ayurvedic, Tibetian, Unioni, traditional faith healing and many others. In general, the last four medical systems can be grouped together and coined as traditional medical system. Among these four, Ayurvedic medical systems has been in force as a major medical system of treatment in Nepal since a long time; but nevertheless traditional faith healers are no less popular. In the rural area, different ethnic groups use a large number of plants and plant products known as Jaributi to prevent or to cure different diseases due to its easy availability and its fewer side effects. In this system of treatment plants and plants products are being used without isolation of active constituents. Hence focused on these medicinal plants with their chemical constituents and their biological activities was the matter of designate since long. Now the book recently published by Prof. Gewali is one of the best book ever published concerning with the Traditional Medicine in Nepal. The book succeeds to cover all most all the aspect of this system of treatment concerning with the scientific facts.

This book aims to introduce basic tenets of the traditional medical system of Nepal. It is intended for the general readers, students and anybody who is interested in Nepali traditional medicine and medicinal plant resources. Written in a simple language and lucid way, it contains four chapters. The first chapter describes the status of existing traditional medicines such as Ayurveda, Homeopathy, Tibetan, Unani, Folk and Shamanistic medicines. The second chapter is devoted to the study of Nepali medicinal plants from the perspectives of utilization, conservation, cultivation, trade and sustainable use. To illustrate the importance of the folk medicines, the third chapter deciphers interesting biological properties and chemical structure diversity in the folk medicines practiced in Manang district of Nepal. The final chapter looks into lingering issues on the safe and effective use of the traditional medicines. Furthermore, the chapter includes the author’s down to earth suggestions for the sustainable development of the medicinal plant resources in Nepal. We appreciate Prof. Gewali and Dr. Suresh for their wonderful work and wish all the best.

Aspects of Traditional Medicine in Nepal (cover page)

Publish at Scribd or explore others: Academic Work professor nepal

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Brief Introduction: Calixarenes

Birendra Babu Adhikari:

Chemical reaction of molecules in specific and selective ways forms the basis of the living world. Taking clue fromthis, chemists have shifted their focus from molecular chemistry to supramolecular chemistry. In majority of cases, the supramolecular architecture is constructed through selective host-guest interactions. [1]

During the molecular evolution of biological system, the highly selective complexation process between the host and the guest must have played a central role. This attribute of biological life was mimicked in synthetic chemistry which later came to be known as the host-guest chemistry. A molecular complex is composed of at least one host and one guest components. The host is an organic molecule or ion whose binding sites converge. The guest is an organic molecule or ion or metal ion whose binding sites diverge [2]. The complexes of the host-guest chemistry are held together in unique structural relationship by forces other than those of covalent nature.

Before the accidental discovery of crown ethers [3] by Pedersen, the word supramolecule was not commonly used; but along with cyclodextrins [4] the crown ethers were also included as another example of host-guest interactions. Later came the discovery of calixarenes [5], which became the third generation of supramolecules. All coexist under the title of supramolecules as well as host-guest chemistry.

In 1872, Adolf von Baeyer heated aqueous formaldehyde with phenol to give a hard resinous product. Three decades later, in 1905–1909, Leo Baekland devised a process and he marketed the strong resin obtained from phenol-formaldehyde, under the name Bakelite. Alois Zinke, a new entrant in this field explored the different possibilities of reacting various p-alkyl phenols with aqueous formaldehyde and sodium hydroxide, and assigned the products of the treatment as cyclic tetrameric structures. These compounds were classed as [1_n]metacyclophanes (where n is the number of benzene rings) Calixarenes are a widely recognized and researched topic in supramolecular chemistry. There were and there are a good number of research groups in the field of calixarene chemistry whose work has already generated hundreds of original journal articles, extensive literature reviews [6-10] and monographs [11] in supramolecular chemistryAlthough worked upon by many before his arrival in this field, the credit of naming this class of compounds goes to C. D. Gutsche, who perceives a similarity between the shapes of these cyclic tetramers and a type of Greek vase known as calix crater (Figure 2). He suggested the compound to be called “Calixarene.”

This “crater” or “basket” plays a very important role in shaping the entire architecture of calixarene for its function in host-guest chemistry. With their well organized and preformed cavities, the calixarenes are able to act as host molecules. Over the years, calixarenes are frequently employed as platforms that permit the design and synthesis of interesting host compounds. Due to such structural elaboration, the calixarenes lend themselves well to many applications.

A series of books and reviews have been published which discuss in length the calixarenes and its substituted derivatives being used for the recognition of cation, anion neutral molecules, and organic moieties [1-13]. The major factor that has contributed for the proliferation of these research papers is the versatile structure of calixarenes for their use as complexing agents. The unlimited possibilities for modification of calixarenes have made them a promising class of host compounds. Their modified potential applications range from their use as selective sensors for different analytical applications and medical diagnostics to their use in decontamination of wastewater, construction of electrodes, and membranes for transportation. The ability in terms of sensitivity and the selectivity of the calixarene as a host to discriminate among a group of guests makes it a special class of subject in supramolecular chemistry. The use of modified calixarenes as sensors for metal ion, organic/neutral molecules, and drugs recognition has brought this class of compounds to limelight and has given the recognition that they enjoy today. They have become a wonder molecule at the hands of a chemist. This wonder molecule has its roots in host-guest chemistry.

References:

1.Lehn, JM. Supramolecular Chemistry. Weinheim, Germany: Springer; 1995.

2．Cram DJ, Cram JM. Design of complexes between synthetic hosts and organic guests. Accounts of Chemical Research. 1978;11(1):8–14.

3.Pedersen CJ. Cyclic polyethers and their complexes with metal salts. Journal of the American Chemical Society. 1967;89(26):7017–7036.

4.Shinkai S. Calixarenes—the third generation of supramolecules. Tetrahedron. 1993;49(40):8933–8968.

5.Gutsche CD, Dhawan B, No KH, Muthukrishnan R. Calixarenes. 4. The synthesis,characterization, and properties of the calixarenes from p-tert-butylphenol. Journal of the American Chemical Society. 1981;103(13):3782–3792.

6.Ikeda A, Shinkai S. Novel cavity design using calix[n]arene skeletons: toward molecular recognition and metal binding. Chemical Reviews. 1997;97(5):1713–1734.

7.McMahon G, O'Malley S, Nolan K, Diamond D. Important calixarene derivatives—their synthesis and applications. Arkivoc. 2003;2003(7):23–31.

8.Sliwa W. Calixarene complexes with transition metal, lanthanide and actinide ions. Croatica Chemica Acta. 2002;75(1):131–135.

9.Menon S, Gidwani MS, Agrawal YK. Chromogenic calixarenes. Reviews in Analytical Chemistry. 2003;22(1):35–51.

10.Böhmer, V.; Shivanyuk, A. Calixarenes in self-assembly phenomena. In: Mandolini L, Ungaro R. , editors. Calixarenes in Action. London, UK: Imperial College Press; 2000. pp. 203–240.

11.Gutsche, CD. Calixarenes. In: Stoddart J. , editor. Monographs in Supramolecular Chemistry. Cambridge, Mass, USA: Royal Society of Chemistry; 1989.

12.Yang W, de Villiers MM. Aqueous solubilization of furosemide by supramolecular complexation with 4-sulphonic calix[n]arenes. Journal of Pharmacy and Pharmacology. 2004;56(6):703–708

13．Ohto K, Yano M, Inoue K, et al. Solvent extraction of trivalent rare earth metal lons with carboxylate derivatives of calixarenes. Analytical Sciences. 1995;11(6):893–902.

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Microwaves as a Reaction Methodology:

Myself.............

There have been many reports of injury to people using microwave ovens to heat water to make hot drinks. Water heated in a microwave oven may be superheated and when objects (e.g. a spoon ) or granulated materials( e.g. instant coffee) are put into it, the water may boil very vigorously or even appear to explode out of the container. The vigorously ejected boiling water can cause serious burns. Sometimes even the act of taking the container out of the oven and or putting it on the bench can cause the boiling. In this condition the water is said to be super heated condition.
It has long been known that molecules undergo excitation with electromagnetic radiation. This effect is utilized in household microwave ovens to heat up food. However, chemists have only been using microwaves as a reaction methodology for a few years. Some of the first examples gave amazing results, which led to a flood of interest in this novel technique.
The water molecule is the target for microwave ovens in the home; like any other molecule with a dipole, it absorbs microwave radiation. Microwave radiation is converted into heat with high efficiency, so that "superheating" becomes possible at ambient pressure. Enormous accelerations in reaction time can be achieved, if superheating is performed in closed vessels under high pressure; a reaction that takes several hours under conventional conditions can be completed over the course of minutes.
Excitation with microwave radiation results in the molecules aligning their dipoles within the external field. Strong agitation, provided by the reorientation of molecules, in phase with the electrical field excitation, causes an intense internal heating. The question of whether a nonthermal process is operating can be answered simply by comparing the reaction rates between the cases where the reaction is carried out under irradiation versus under conventional heating. In fact, no nonthermal effect has been found in the majority of reactions, and the acceleration is attributed to superheating alone. It is clear, though, that nonthermal effects do play a role in some reactions.
Unmodified home microwave units are suitable in some cases. However, simple modifications (for example, a reflux condenser) can heighten the safety factor. High-pressure chemistry should only be carried out in special reactors with a microwave oven specifically designed for this purpose. A further point in favor of using the more expensive apparatus is the question of reproducibility, since only these specialized machines can achieve good field homogeneity, and in some cases can even be directed on the reaction vessel.

Organic chemistry portal

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Synthesis and structures of [2.n]metacyclophane-1,2-diones using McMurry Cyclisation and Albright-Goldman oxidation

My side project; just enjoying some reactions:

Last few days I was busy in writing annual report, complete my project and enjoying New Year 2009. Therefore I could not write any things in this site. This time I have intended to write about some reactions that I have done myself. This is not my major field but I enjoy doing reactions and explain the structure of some theoretically important compounds.

As you might be known that cyclophane chemistry field is quite popular since long for its theoretical beauty, structural pattern and scope of versatile use of reactions within the structure. Different kinds of chemical aspect can be studied within a single molecule. For organic chemistry student those trying to understand synthesis of organic compounds and willing to act upon different types of reactions should make good practice over certain compounds which I think is the best way to learn. So I used go with cyclophane type of compounds just for enjoying chemical reactions. I hope you will enjoy these reactions too………………….
Here, I have developed a convenient preparation of a series of syn- and anti-[2.n]MCP-1-enes 4 and [2.n]MCP- 1,2-diols 5 by a McMurry cyclisation of 1,n-bis(5-formyl-2-methoxyphenyl)alkanes 3. Also, [2.n]MCP-1,2-diols 5 were converted to the 1,2-diones 7 by Albright-Goldman oxidation.

Reaction scheme:


Further
Finally

Don’t you think that playing with these kind of reactions will be better to understand the synthesis chemistry in an easy way? It is just an example . I just tried it out and experienced. I hope you enjoy it…

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