Why do the bromine test, when subjected to sunlight produces an evolution of hydrogen bromide?
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The bromination of a double bond is a reaction which proceeds with trans addition of bromine, where two bromine atoms add to the alkene from opposite faces of the molecule (see Brown & Foote, Ch. 6). In the addition of bromine to E-stilbene, the resulting compound is meso-stilbene dibromide (m-2,3-dibromo-2,3-diphenylethane), \n Trans Addition of Bromine to E-Stilbene.\nA meso compound contains chiral or asymmetric carbon atoms and is superimposable upon its mirror image.\n\n \nIn meso-stilbene dibromide, both C1 and C2 are asymmetric carbon atom. It has an internal plane of symmetry, bisecting the molecule into two halves about the C1 and C2 bond. Similiar to a racemic mixture, meso compounds are optically inactive.\n\n[Recall: the lack of optical activity in a racemic mixture is due to the fact that any optical rotation produced by one molecule is cancelled by another molecule which is a mirror image of the first. Since a mirror image produces an equal and opposite rotation, the presence of equal amounts of each enantiomer leads to an overall optical rotation of zero.]\n\nFor a meso compound, one half of the molecule is the mirror image of the other half, and so any optical rotation caused by asymmetric centre, C1, of meso-stilbene dibromide is cancelled by an equal and opposite effect at the other asymmetric centre, C2. The overall result is therefore a net optical rotation of zero.\n \n\n\n2. Conversion of meso-Stilbene Dibromide to Diphenylacetylene.\n\nAlkynes are commonly prepared by the dehydrohalogenation of 1,2-dihalides under basic conditions. Normally, a very strong base such as sodamide (NaNH2) is necessary, but treatment of meso-stilbene dibromide with potassium hydroxide leads to the formation of diphenylacetylene in high yield.\n\n\n\nPart B: Properties of Alkanes & Alkenes.\n\nThere are a number of simple tests that may be used to differentiate alkanes from alkenes or to detect the presence of alkenes in alkanes. These tests are based upon the reactivity of alkenes with a variety of reagents to which the alkanes are insensitive. Use cyclohexene as a typical alkene, ligroin (petroleum ether, mostly hexanes) boiling at 66-75 oC as a typical mixture of alkanes, and unpurified ligroin as an impure alkane.\n\n\n--------------------------------------------------------------------------------\n\nPRE-LAB PREPARATION: \n\n1. Draw the products of bromination of Z- and E-2-butene. Specify which (if any) of these products is optically active. Are any of the structures identical?\n\n2. In the bromination of Z-stilbene, would any of the products be meso compounds? Explain.\n\n3. When performing chemical tests (Part B), it is useful to understand how (and if) test reagents react with certain functional groups. Write general equations for the bromination of alkanes and alkenes. Write a general equation for the oxidation of alkenes by potassium permanganate.\n\n\n--------------------------------------------------------------------------------\n\nEXPERIMENTAL PROCEDURE: \n\nStart with Part A and perform the tests in Part B as time permits during the lab (you should finish both Parts A & B by the end of the lab).\n\nCaution! Both bromine and acetic acid are noxious liquids which should be handled with extreme care. Bromine is highly volatile, toxic, and causes severe skin burns. In case of spillage onto the skin, the affected area should be washed immediately with water.All work with bromine or bromine solutions must be performed in the fume hood. \n\nPart A: Preparation of meso-Stilbene Dibromide and its Conversion to Diphenylacetylene. \n\n\nThis experiment is conducted using microscale equipment. You should review the procedures for the use of this type of equipment which is contained in the Microscale Techniques section of the lab manual.\n\n1. Addition of Bromine to E-Stilbene\na) Weigh out 230 mg of E-stilbene into a 10 mL cylindrical vial, add 2.2 mL of acetic acid.  Equip the vial with a magnetic stir bar and a water con
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Bromine gas is reddish-brown, at times described as orange. However, when it exists as ions (bromide ions, Br-), it is colourless.
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First, you can't change the bonds unless you replace one or both of the atoms involved in the bond.  Second, it's the halogen radicals (Cl and F) that are (supposedly) the problem.  If you start replacing the halogens with other kinds of elements, you will lose the molecular properties that made CFCs so useful to begin with.  \n\nI wonder what, if any, effect a higher UV flux would have on the mutation rate here on the surface of the Earth.  What kinds of changes do you think might occur?  This might be a good topic for your project.  And the best part is that no one can prove you wrong...
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Couple of things come to mind. 1) pH and/or total alkalinity are out of sorts. Check with a reliable test kit and adjust accordingly. 2) If it is a chlorine pool you may have a sensitivite to chlorine. Lots of people do. Curious, though, that it is only on your face? If you are using sunscreen on your face prior to swimming perhaps it is the sunscreen. Look for something like that, too.
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H2, or hydrogen gas.\n\nFor example, take magnesium metal and hydrochloric acid.\n\nMg + 2HCl -> H2 + MgCl2\n\nThis is a displacement reaction, in which a free element (Mg) breaks the bond between a compound (HCl) and then bonds to the ion with the opposite charge (Cl-) forming a new compound (MgCl2).  The ion left over (H+) loses its charge and becomes a pure element (H2).
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The sunlight gives cllorphyl a pigment to turn green when thiers less sun the other pigments reflect because the subnlight is not as strong as b4
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Sun has a nuclear reaction (fission of Hydrogen gas)to radiate energy. Theoratically as much as Hydrogen is being used in the process of energy production the net quantity of hydrogen is being reduced and so net amount of reacting atoms is decreasing. Thus energy of sun is being reduced. However, the rate of decrease in the active mass is so slow that it can not be measured in course of few centuries.\n\nThe much referred worming of air or global worming, as replied here by one other, is due to increasing pollution of air or green effect.
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Let me be the first to say this is a diabolical question that has led me on a merry chase through the Internet. Not having a virtual lab with both chemicals on hand, I consulted Erik B., a chemical engineer from Purdue, to get your answer. We discovered that there are many variables with this compound; your product is determined by the quantities of each chemical that you use. On one hand, you can produce a completely colorless form of silver that has been used in the past as a discrete poison. The most common product of this compound, however, is SILVER CHLORIDE [silver chloride] chemical compound, AgCl, a white cubic crystalline solid. It is nearly insoluble in water but is soluble in a water solution of ammonia, potassium cyanide, or sodium thiosulfate ( "hypo" ). On exposure to light it becomes a deep grayish blue due to its decomposition into metallic silver and atomic chlorine. This light-sensitive behavior is the basis of photographic processes. Since silver bromide, AgBr, and silver iodide, AgI, react similarly, all three of these silver halide salts are used in making photographic films and plates. Both the bromide and iodide are less soluble in water and more sensitive to light than the chloride. The bromide forms light yellow cubic crystals; the iodide forms yellow hexagonal or yellow-orange cubic crystals, depending on the temperature. Besides use in photography, silver chloride is used in silver plating, and silver iodide is used for seeding clouds. The chloride, bromide, and iodide occur naturally as the minerals cerargyrite, bromyrite, and iodyrite, respectively. Silver fluoride, AgF, forms colorless cubic crystals; it is much more soluble in water than the other silver halides. Incidentally, should you wish to try the home-grown poison, just like for photos, silver oxide gathers in the skin and reacts with light, creating a bluish-gray tint that is a clear signal of foul play. *Don't* try this at home.\n\nHappy Answering,\n~Tia~\nLive from the big, purple brain\nhttp://advision.webevents.yahoo.com/asktheplanet/brain.html\nASK YOUR QUESTIONS, CALL THE BRAIN - 212-382-3592
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Sunlight is a particle.
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The traditional method of measuring unsaturation is to measure the reaction between the substance and a solution of molecular bromine.  The Br2 adds across double bonds that are present and you can measure the change in color of the bromine solution.  \n\nA less toxic (but more explosive) alternative is to hydrogenate the substance with a known quantity of hydrogen gas and measure the change of pressure, volume, or mass to determine how much hydrogen has been incorporated.
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The sun gives us light because of nuclear fusion-two atoms of Hydrogen are combining in huge quantities to form one atom of Helium. The mass of two atoms of Hydrogen are slightly more than one atom of Helium, which is mono atomic.The difference in this mass is converted to energy in the form of Heat and Light, rays of which don't need a medium to travel.
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I think it happens from an excess of silicon and suns rays. Oh, and drugs, lots of drugs. I don't know, I am just hanging around here to see what kind of answers you get.
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D) reducing agent\n\nBr2 is neutral,whereas Br- is negatively charged (There has been an addition on of electron).Electron gain is reduction.So Br2 has been reduced.\nHence Sodium bisulfite is a reducing agent.
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During photosynthesis, light energy is converted into chemical potential energy.
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UV light directly causes DNA damage.  Causes formation of thymine dimers.
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Sun poisoning is most likely to occur during hot seasons when ultraviolet light is strongest. It's triggered by exposure to the sun, usually combined with sunburn. It's especially likely in children who take medications that cause photosensitivity. The most common drugs include tetracycline antibiotics, thiazide diuretics, sulfa drugs, and oral contraceptives. It's not a precursor to skin cancer, so don't worry. Of course, long-term exposure to the sun can cause skin cancer, but just because you get sun poisoning doesn't mean your'e going to get cancer.
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It is hydrogen (H). Hydrogen must always exist as a compound, forming a covalent bond with another hydrogen atom (H2).\n\nAtoms such as this are called 'diatomic'. There are others (N, O, F, Cl, Br, and I), however, only H is the stuff of the sun.\n\nUse the extra info to dazzle your teacher.\n\n. . .  and if you didn't know, now you do . . .