Top Document: Sci.chem FAQ - Part 4 of 7 Previous Document: 17. Preparation of chemicals See reader questions & answers on this topic! - Help others by sharing your knowledge 18.1 How do light sticks work?, and how can I make one? From: perks@umbc.edu (Mark Perks) Date: 15 Sep 1994 Subject: Re: Chemiluminescence Sticks Chemical Demonstrations [[1] v.1 p.146- ], by Bassam Shakhashiri, offers a thorough discussion of Cyalume lightsticks. Professor Shakhashiri is at the University of Wisconsin, Madison, I believe. "The Cyalume lightstick contains dilute hydrogen peroxide in a phthalic ester solvent contained in a thin glass ampoule, which is surrounded by a solution containing a phenyl oxalate ester and the fluorescent dye 9,10-bis(phenylethynyl)anthracene...When the ampoule is broken, the H2O2 and oxalate ester react.." From: chideste@pt.Cyanamid.COM (Dale Chidester) Date: Mon, 13 Mar 1995 Subject: Re: How to make chemical light ? The following produce rather spectacular results. Chemicals are available through Fluka and Aldrich. The dyes are expensive. Dyes:- 9,10-bis(phenylethynyl)anthracene (BPEA) (yellow) [10075-85-1] Fluka 15146 9,10-diphenylanthracene (DPA) (blue) [1499-10-1] Fluka 42785 5,6,11,12-tetraphenylnaphthacene (rubrene) (red) [517-51-1] Fluka 84027 Other reagents required:- bis(2-carbopentyloxy-3,5,6-trichlorophenyl)oxalate (CPPO) [75203-51-9] Aldrich 39,325-8 bis(2-ethylhexyl)phthalate (DOP) (solvent) [117-81-7] Fluka 80032 sodium salicylate (catalyst) [54-21-7] Fluka 71945 35% hydrogen peroxide [7722-84-1] Fluka 95299 Saturate solvent with dye and CPPO. Sonicate to help solvation. Start with about 50 mg dye (BPEA, DPA or rubrene) in 10 g solvent with 50 mg CPPO and 5 mg sodium salicylate. CPPO is limiting reagent. Put small quantity (20 drops) in a small vial and add equal volume of hydrogen peroxide. Mix vigorously. There will be two phases. Avoid skin contact! Don't cap tightly! The following explanation of the chemistry was provided:- From: sbonds@jarthur.claremont.edu (007) All of the material below is taken from a chemical demonstrations book [[1], v.1, p.146 ]. The oxidant is hydrogen peroxide contained in a phthalate ester solvent. The concentration is very low, less than 0.5%. The fluorescing solution consists of a phenyl oxalate ester and a fluorescent dye. The dye used is 9,10-bis-(phenylethynyl)anthracene (for green) or 9,10-diphenylanthracene (for blue). Here is the reaction sequence: 1) (Ph)-O-CO-CO-O-(Ph) + H2O2 --> (Ph)-O-CO-CO-O-OH + (Ph)-OH 2) (Ph)-O-CO-CO-O-OH --> O-O | | + (Ph)-OH OC-CO 3) C2O4 + Dye --> Dye* + 2CO2 4) Dye* --> Dye + hv In 1) The hydrogen peroxide oxidizes the phenyl oxalate ester to a peroxyacid ester and phenol. The unstable peroxyacid ester decomposes to the cyclic peroxy compound and more phenol in step 2). The cyclic peroxy compound is again unstable and gives off energy to the dye as it decomposes to the very stable carbon dioxide. The dye then radiates this energy as light. An alternative chemiluminescence demonstration involves the H2O2 oxidation of lucigenin ( bis-N-methylacridinium nitrate [2315-97-1] Aldrich B4,920-3 ), [ [1] v.1 p.180-185 ] which has recently been modified to provide a slow colour change across the visible spectrum [2]. One of the reagents in that lucigenin oxidation ( Rhodamine B ) is a mutagen and suspected carcinogen. 18.2 How do hand warmers work?, and how can I make one? They consist of an aqueous solution of sodium acetate with a small "clicker" disk to provide a small clean surface that initates crystallisation. The solute is dissolved into solution by prior warming. When heat is required, the disk is "clicked" to scrape a small surface, and this clean surface will initiate the sodium acetate crystallisation from the now supersaturated solution. The heat of crystallisation is slowly released. 18.3 What are the chemicals that give fruity aromas? Most of the desirable food aromas come from low to medium molecular weight organic compounds - usually alcohols, aldehydes, esters, ketones, and lactones. These may be " natural " ( extracted from natural sources ), " nature-identical " ( synthetic, but identical to known natural compounds ), and " artificial " ( synthetic, not found in nature ). The perceived aroma of molecules can change dramatically with minor isomeric or structural changes, and common fruity aromas are usually complex mixtures of several compounds. Because man-made chemicals are frequently made from chemicals derived from fossil fuels, the isotopic ratios of the carbon atoms has been used to discriminate between natural and nature-identical chemicals. Natural processes usually involve the use of enzymes that selectively produce a specific isomer, and some man-made aromas are now produced enzymatically. Chiral chemistry, often utilising chiral chromatography that was initially developed for pharmaceuticals, is now also being used for the production and testing of man-made aromas, as enantiomerically-pure aroma chemicals command premium prices. Some chemicals are listed below, along with their use in either fragrances and/or flavours, and boiling point ( 760 mmHg, unless otherwise stated ). Some of them are also considered toxic, and thus their use may be controlled. Volume A11 of Ullmann has an excellent monograph on flavours and fragrances, and more detail can be obtained from the journal Perfumer and Flavorist. The catalogues of well-known suppliers such as Dragoco GmbH ( Germany ), L.Givaudin and Cie ( Switzerland ), and Takasago Perfumery Company ( Japan ), also contain information on chemical composition and health and safety. Chemical BP CAS RN Application C (mmHg) acetoin 148 [513-86-0] butter acetophenone 202 [98-86-2] orange blossom benzyl acetate 206 [140-11-4] jasmine butyl acetate 125 [123-86-4] apple 2,3-butanedione 88 [431-03-8] butter (+)-carvone 230 [2244-16-8] caraway, dill (-)-carvone 230 [6485-40-1] spearmint citral 229 [5392-40-5] lemon citronellal 207 [2385-77-5] balm mint decanal 208 [112-31-2] citrus dihydromyrcenol 78 (1) [18479-58-8] lavender 2,6-dimethyl-2-heptanol 171 [13254-34-7] freesia ethyl butyrate 120 [105-54-4] pineapple ethyl 2t-4c-decadienoate 71 (45) [3025-30-7] pear ethyl hexanoate 168 [123-66-0] pineapple ethyl isovalerate 132 [108-64-4] blueberry ethyl 2-methylbutyrate 133 [7452-79-1] apple geraniol 229 [1066-24-1] roselike hexyl acetate 169 [142-92-7] pear hexyl salicylate 168 (12) [6259-76-3] azalea 1-(4-hydroxyphenyl)-3-butanone [5471-51-2] raspberry isoamyl acetate 143 [123-92-2] banana (+)-limonene 176 [5989-27-5] lemon linalool 198 [78-70-6] lily of the valley linalyl acetate 220 [115-95-7] bergamot 8-mercapto-p-menthan-3-one 57 (8) [38462-22-5] blackcurrant 1-p-methene-8-thiol 40 (1) [71159-90-5] grapefruit 3-methyl-2-cyclopenten-2-ol-1-one [80-71-7] caramel 4-methyl-2(2-methyl-1-propenyl)tetrahydropyran 70 (12) [16490-43-1] rose myrcenol 78 (50) [543-39-5] lime 2t-6c-nonadien-1-ol 98 (11) [28069-72-9] violet 3-octanol 175 [20296-29-1] mushroom 1-octen-3-ol 84 (25) [3391-86-4] mushroom phenethyl acetate 238 [103-45-7] rose phenethyl alcohol 220 [60-12-8] rose phenethyl isoamyl ether [56011-02-0] chamomile 2-propenyl hexanoate pineapple alpha-pinene 156 [80-56-8] pine alpha-terpineol 217 [98-55-5] lilac alpha-trichloromethylbenzyl acetate [90-17-5] rose 18.4 What is the most obnoxious smelling compound? Many low molecular weight sulfur-containing compounds tend to induce adverse reactions in people, even if they have not encountered them before, eg the glandular emissions of skunk (n-butyl mercaptan, dicrotyl sulfide). Butyric acid reminds people of vomit, and cadaverine ( 1,5 Pentadiamine ) reminds people of rotten tissue, but without an earlier association, they may not regard them as unusually obnoxious. 18.5 What is the nicest smelling compound? Aside from thinking about your stomach, when the smell of cooking foods is attractive, then most people like the smell of flowers and citrus fruits. These are volatile, aromatic, oils, whose major components are complex mixtures of medium volatility compounds, often derived from terpenes, eg Oil of Rose ( 70 - 75% geraniol = (E)-3,7-dimethyl-2,6-octadiene-1-ol ), Oil of Bergamot ( 36 - 45% linalyl acetate = 3,7-dimethyl-1,6-octadien-3-yl acetate ). Many aromatic oils are mixtures of terpene esters ( oil of geranium = 20 - 35% geraniol esters ) or aldehydes ( oil of lemon grass = 75 - 85% citral = 3,7-dimethyl-2,6-octadienal ). Merck briefly describes nearly 100 volatile oils, from Oil of Amber to Oil of Yarrow, along with typical applications. Flower perfumes are complex blends of compounds, and detailed compositions of your favourite smell are often available in the journal " Perfumer and Flavorist ". Expensive flower petal perfumes, such as rose and jasmine, are produced using extracts obtained by the traditional "enfleurage" process ( refer to Section 24.4 ). User Contributions:Top Document: Sci.chem FAQ - Part 4 of 7 Previous Document: 17. Preparation of chemicals Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: B.Hamilton@irl.cri.nz
Last Update March 27 2014 @ 02:12 PM
|
Comment about this article, ask questions, or add new information about this topic: