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Topic: Dehydration reaction

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	Condensation reaction - Wikipedia, the free encyclopedia
		A condensation reaction (also known as a dehydration reaction or dehydration synthesis when water is lost) is a chemical reaction in which two molecules or moieties react and become covalently bonded to one another by the concurrent loss of a small molecule, often water, methanol, or a type of hydrogen halide such as HCl.
		It may be considered as the opposite of a hydrolysis reaction (the cleavage of a chemical entity into two parts by the action of water).
		The reactions that form acid anhydrides from their constituent acids are typically condensation reactions.
	en.wikipedia.org /wiki/Dehydration_synthesis (377 words)

	Intramolecular Dehydration
		In this reaction the alcohol is heated in the presence of sulfuric acid.
		Those earlier ionic reactions were taking place in aqueous solution where the concentration of water was so large (about 55 moles per liter) that the formation or reaction of water had very little effect upon the position of equilibrium.
		As I pointed out earlier, this kind of dehydration reaction in which you form an alkene from an alcohol is called intramolecular dehydration because all of the atoms for the water molecule came from the same alcohol molecule.
	dl.clackamas.cc.or.us /ch106-03/intramol.htm (541 words)

	Biochemistry (Site not responding. Last check: 2007-11-02)
		Reaction (i) is an exchange, irreversible reaction (note that ATP is hydrolyzed) that is catalyzed by the enzyme hexokinase.
		Reaction (ii) is a reversible reaction catalyzed by the enzyme phosphoglucose isomerase.
		Reaction (iii) is another exchange, irreversible reaction (again, note that ATP is hydrolyzed) that is catalyzed by the enzyme phosphofructose kinase.
	www.mansfield.ohio-state.edu /~sabedon/biol1020.htm (2119 words)

	Dehydration By Alcohol Facts \| Dehydration By Alcohol Information (Site not responding. Last check: 2007-11-02)
		Dehydration alcohol is a diuretic alcohol consumption increases urination, and causes your body to become dehydrated.
		Dehydration call kill much faster than starvation, she said, pointing to how a 10 loss of body fluids can be critical, and a 20 loss results in death.
		Signs of dehydration particularly reduced skin turgor and orthostatic hypotension are often present in normally hydrated older people 1, 2 and so have a limited sensitivity and specificity in diagnosing mild and moderate dehydration during the initial assessment of new patients 3, 4.
	www.dehydration-study.info /dehydration-by-alcohol.html (964 words)

	U.S. Patent: 5304624 - Epoxy resin derived from the highly pure compound and method for preparing the resin and ...
		The dehydration-condensation reaction may likewise be performed in such a solvent by dissolving BXF in the solvent and then performing the reaction while blowing air or oxygen through the reaction solution.
		In the dehydration-condensation reaction, it is preferred that the water formed through the reaction be continuously removed and discharged out of the system through an apparatus fitted to a reactor such as a reflux condenser irrespective of the foregoing conditions.
		In the epoxidation reaction, the epihalohydrin is used in an excess amount ranging from 2.0 to 30 equivalents, preferably 2.0 to 10 equivalents per equivalent of OH group of the TKXE.
	www.everypatent.com /comp/pat5304624.html (3718 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		Dehydration is an acid catalyzed elimination reaction involving the loss of H
		The mechanism of the dehydration reaction is given for 1-methylcyclohexanol in McM Figure 17.5.
		From this point on the reaction is an E-1 elimination involving carbocation intermediate.
	science.csustan.edu /almy/3012/Dehydration.htm (1228 words)

	eassignmenttwo
		The mechanism of dehydration of an alcohol was studied in terms of the stability of the alkene formed.
		The dehydration of an alcohol is a reversible reaction with the reverse reaction being the addition of water to an alkene to form an alcohol.
		These two addition reactions indicate the presence of a double bond by visible changes in the color (colored to colorless) of the two reactants used in the separate tests - bromine, which is reddish brown and potassium permanganate, which is deep purple.
	www.sas.upenn.edu /~cutillo/eassignmenttwo.html (576 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		The reaction system of tert-butanol/isobutene/water was considered for use in chemical heat transport.
		In this study, the heat-transfer characteristics in an endothermic tert-butanol dehydration reaction which occurred in the heat-supply side of this reaction system was investigated.
		These results indicated that the dehydration reaction promoted the heat-transfer rate, because of the increase in temperature difference between the heating medium and the wall by making use of chemical reaction for a heat transport.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=276278 (302 words)

	F25. Kinetic and Thermodynamic of 2-Propanol Dehydration Reaction In Supercritical Water (Site not responding. Last check: 2007-11-02)
		Kinetic and mechanism of 2-propanol dehydration reaction in supercritical water (SCW) in the batch reactor are investigated.
		Was shown, first, that the mechanism of the dehydration reaction essentially differs from the reaction mechanism at the presence of the homogeneous acid catalyst, secondly, the rate of reaction depends considerably from the SCW density.
		Kinetic of 2-propanol dehydration reaction investigated, the values of the first-order rate and equilibrium constants are found.
	www.cstl.nist.gov /div838/kinetics2001/agenda/f_session/f25/f25.htm (195 words)

	Chemistry 210 Experiment 6
		As a result, reaction would be expected to proceed via the E2 elimination mechanism for any primary alcohol.
		There is one more event that is possible in a reaction that involves carbocation intermediates, and is even a possibility with the E2 reaction shown for 1-pentanol, and that is rearrangement.
		It is also possible that the 1° alkyloxonium ion formed by the protonation of 1-pentanol has the potential to rearrange via a 1,2-hydride shift (which kicks off the water molecule as the leaving group).
	www.miracosta.cc.ca.us /home/dlr/210exp6.htm (1795 words)

	Transition Metal Catalysed 1-Oxa-1,3-diene Formation (Site not responding. Last check: 2007-11-02)
		At 80°C, where all the metal catalysed reactions were performed, the thermal dehydration is hardly proceeding at all (4% conversion, entry 2) and can thus be neglected as competing reaction.
		As obvious from the iodine catalysed dehydration reaction (entry 5, Table 1a) proceeding under thermodynamic control, the conjugated and non-conjugated enones 2 and 3 are of very similar stability.
		As a mechanistic explanation for the observed dehydration regioselectivity, formation of hydroxo-metal intermediates and subsequent abstraction of a proton from the sterically less hindered, i.e.
	www.ch.ic.ac.uk /ectoc/papers/07 (2969 words)

	Gypsum under fire:
		The dehydration of gypsum under heat exposure is well recognized, although not fully characterized quantitatively due to its inherent complexity.
		For the first dehydration reaction, the temperature is generally agreed around a range of 80-125 or 100-125C (although low dehydration temperature as low as 75C is observed).
		This is due to the fact that gypsum is a porous material with variable thermal properties associated with the moisture migration, further complicated by the two endothermic reactions associated with the dehydration processes.
	www.glue.umd.edu /~tgma/Gypsum.htm (1697 words)

	Explaining the dehydration of ethanol to give ethene
		Dehydration of more complicated alcohols is dealt with on a separate page.
		In the second stage of the reaction the protonated ethanol loses a water molecule to leave a carbocation (previously known as a carbonium ion) - an ion with a positive charge on a carbon atom.
		AQA (the only Exam Board to demand the dehydration mechanism at the moment) is happy to accept this version.
	www.chemguide.co.uk /mechanisms/elim/dhethanoltt.html (626 words)

	Nucleotide Variations
		However, it is a dehydration reaction whether the water molecule is shown or not.
		These dehydration reactions, or condensation reactions as they are sometimes called, can also be viewed as phosphorylation reactions because they involve attaching a phosphate unit to an existing molecule.
		The tendency for these reactions to occur and provide or release energy is used by a number of enzymes to catalyze reactions which require energy.
	dl.clackamas.cc.or.us /ch106-09/nucleoti1.htm (565 words)

	Jack's Demos 92-101
		Iodine Clock Reaction is one of the classic illustrations of the time rate of change of concentration of reactants characteristic of chemical reactions.
		One reaction of special interest because of its importance to organic chemistry is the dehydration reaction.
		In this reaction, cumene hydroperoxide, a reaction intermediate in the commercial synthesis of phenol and acetone, two important industrial chemicals used for everything from pharmaceuticals to polymers, is decomposed in the presence of a trace of acid (which is the initiator).
	www.columbia.edu /itc/chemistry/chem-c140498/jack/ch14.html (590 words)

	The Structure and Function of Macromolecules (Site not responding. Last check: 2007-11-02)
		Dehydration reaction is synonymous with condensation reaction except that dehydration reaction is limited to those condensations in which the small molecule is water
		The most important thing to understand about dehydration synthesis is why it is named what it is (i.e., dehydration synthesis or condensation reaction).
		An example of such a reaction is the binding of two phosphates together, e.g., as in the reaction ADP + Pi --> ATP + HOH.
	www.mansfield.ohio-state.edu /~sabedon/campbl05.htm (1681 words)

	HJIC 1977, 5(1), 1-96
		Krishnaprasad T. and Ravindram M. Catalytic vapour phase dehydration of ethyl alcohol was studied in a fixed bed reactor in the temperature range 300-375 Celsius, over Linde molecular sieves 10x, 13x and 5A.
		Acidity of the catalyst was found the influence the dehydration activity of the catalyst.
		The dependence of eta on the supposed linear velocity of gas and liquid was determined by corresponding measurements.
	www.vein.hu /HJIC/content/v05n1.html (1169 words)

	Chapter 5
		Monomers are connected together by a reaction in which 2 molecules are covalently bonded to each other through loss of a water molecule.
		Called a dehydration reaction b/c a water molecule is lost.
		Those cells can then use dehydration reactions to assemble the monomers into new polymers that differ from the ones that were digested.
	bama.ua.edu /~kcaldwel/Chapter05.html (2089 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		The mechanism of the dehydration reaction is given for 1-methylcyclohexanol in McM Figure 17.6.
		Let us assume that the 2-butyl carbocation formed during the reaction of 1-butanol undergoes the same fate as if it were formed from 2-butanol.
		Calculate your difference in activation energy for the two competing reactions of 1-butyl carbocation.
	wwwchem.csustan.edu /chem3012/Dehydration.htm (1272 words)

	JCE 1999 (76) 826 [Jun] A Puzzling Alcohol Dehydration Reaction Solved by GC-MS Analysis
		We have adapted the dehydration of 2-methyl-2-propanol to a "puzzle" approach for use in our second-semester chemistry major organic laboratory.
		The reaction of 2-methyl-2-propanol with ~50% sulfuric acid at 100 °C yields isobutylene, which reacts further by a "puzzling" reaction.
		By coupling the GC/MS analysis of the product mixture with their knowledge of the mechanism of alcohol dehydration and alkene reactivity, students are able to identify the major products of this reaction.
	jchemed.chem.wisc.edu /Journal/Issues/1999/Jun/abs826.html (144 words)

	C-C bonds
		However, the reaction requires that the diene be electron-rich and the dienophile electron-poor.
		The C(sp) of the nitrile is synthetically equivalent to a carbonyl C. Aldol reaction
		The C(sp) of the nitrile is synthetically equivalent to a carbonyl C. Aldol–dehydration reaction
	www.chem.uky.edu /courses/che232/RBG/handouts/CC_bonds.html (2180 words)

	experiment1
		A characteristic reaction of alkyl halides is that they undergo elimination reactions to give alkenes.
		The overall reaction is a dehydration of the original substrate and
		The mechanism of this dehydration reaction is shown above and involves the same carbocationic intermediates noted earlier for the dehydrobromination reaction
	www.wiu.edu /users/mftkv/Chem332/experiment1.html (812 words)

	Green Chemistry Lab Database
		An organic chemistry laboratory experiment involving an equilibrium dehydration reaction where two hydroxyl groups of a tetra-alcohol, pentaerythritol, react with benzaldehyde in aqueous acid to form a benzal, 5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxiane (an acetal derived from benzaldehyde) is described.
		This reaction can be used to illustrate the mechanism for the formation of ketals (and acetals) and their use as protecting groups for ketones (and aldehydes).
		The temperature sensitivity of this reaction also enables this experiment to be used as a group exercise to illustrate optimization of reaction conditions to maximize product yield.
	darkwing.uoregon.edu /~greenlab/Pages/OC-0001.htm (190 words)

	Current/New Research Projects: (Site not responding. Last check: 2007-11-02)
		Most notably, 4-phenyl-1-butanol undergoes elimination like its isomers but the major reaction pathway is Friedel-Crafts alkylation (a new reaction for our students to discover).
		Ideally, half of the class would do a dehydrohalogenation reaction (E2) while the rest conducts a dehydration reaction (E1).
		Ideally, this would be contrasted to addition reaction that do not proceed by carbocation intermediates and that lead to the opposite orientation
	www.holycross.edu /departments/chemistry/brochure/ron (306 words)

	Partial thermodynamic equilibrium and Gibbs energy minimisation (Site not responding. Last check: 2007-11-02)
		And now, the problem is: the equilibrium calculated from this last reaction tends to assign the gypsum to the hot region at the expense of the gypsum in the cold region.
		You might want to refresh your memory as far as enthalpies of reaction --- or, do a little dinosaur hunting (mixing plaster for jacketing bones) --- you are examining a system that exhibits counter-intuitive behavior.
		But, please, note that it is not the system that exhibits a strange behaviour: the hot gypsum (90°C) dehydrates in the center of the silos and the water vapor recombines with the hemihydrate (or plaster) in the cold region of the silos (there are no dinausor artifact there, but that doesn't matter).
	www.physicsforums.com /showthread.php?p=977842#post977842 (1345 words)

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