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Substituent - Wikipedia, the free encyclopedia In organic chemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. Additionally, when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent is attached to when such information is needed to distinguish between structural isomers. The polar effect exerted by a substituent is a combination of the inductive effect and the mesomeric effect. en.wikipedia.org /wiki/Substituent   (310 words)

Nomenclature Examples When one substituent and one hydrogen atom are attached at each of more than two positions of a monocycle, the steric relations of the substituents may be expressed by first identifying a reference substituent (labeled r) followed by a hyphen and the substituent locator number and name. When two different substituents are attached at the same position of a monocycle, then the lowest-numbered substituent named as a suffix is selected as reference group. If none of the substituents is named as a suffix, then that substituent of the pair of substituents having the lowest number, and which is preferred by the sequence rule, is chosen as the reference group. www.cem.msu.edu /~reusch/VirtualText/nomexmp1.htm   (1823 words)

Amide and urea derivatives having anti-hypercholesteremic activity, their preparation and their therapeutic uses - ... In the case of the groups of formula (II), preferred substituents are the alkyl and alkoxy groups having 1 or 2 carbon atoms and the halogen atoms, especially the methyl and methoxy groups and the chlorine and bromine atoms, more preferably the methoxy group and the chlorine and bromine atoms. In the case of the groups of formula (III), preferred substituents are the alkyl and alkoxy groups having 1 or 2 carbon atoms and the halogen atoms, especially the methyl and methoxy groups and the chlorine and bromine atoms. In the case of the groups Of formula (IV), preferred substituents are the alkyl and alkoxy groups having 1 or 2 carbon atoms and the halogen atoms, especially the methyl and methoxy groups and the chlorine and bromine atoms, more preferably the methoxy group and the chlorine and bromine atoms. www.freepatentsonline.com /5614550.html   (9378 words)

PHA 4220 - Neurology Pharmacotherapeutics Methyl is the optimal substituent for agonist activity, and ethyl is passable. If the nitrogen substituent is a bulky alkyl group such as propyl, isobutyl, or especially allyl and cyclopropylmethyl, the compound becomes a narcotic antagonist. R1 and R2 substituents must be present to supply vestiges of the C ring. wiz2.pharm.wayne.edu /module/opioid.html   (1790 words)

Alkane Nomenclature Groups attached to the parent chain are called substituents and are named based on the number of carbons in the longest chain of that substituent, and are numbered using the number of the carbon atom on the parent chain to which they are attached. In simple alkanes, substituents are called alkyl groups and are named using the prefix for the number of carbons in their main chain and the suffix... If the same substituent occurs more than once in a molecule, the number of each carbon of the parent chain where the substituent occurs is given and a multiplier is used to indicate the total number of identical substituents; i.e., dimethyl... www.chem.uic.edu /web1/ocol/SB/2-1.htm   (821 words)

UNODC - Bulletin on Narcotics - 1958 Issue 4 - 006 Ro 4-0554, in which the substituent was phenylpropargyl, had no analgesic action in mice or rats; it was not tried in rabbits. The effect of the addition of a substituent on the benzene ring of N-phenethyl in this series varied with the nature of the substituent and with the position of its substitution, though such variations were most apparent in the Bethesda observations. In the four pairs of compounds which had the same substituent on nitrogen but in which one had hydroxy and the other methoxy in the 3-position, the methoxy was much weaker than the hydroxy derivative, as is the case in the methorphan-levorphanol pair and in the codeine-morphine pair. www.unodc.org /bulletin/bulletin_1958-01-01_4_page007.html   (2625 words)

Class Definition for Class 564 - ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES Compounds wherein the sulfur is part of a substituent which is monocyclic and aromatic. The substituent nitrogen is attached indirectly to the benzene ring by acyclic nonionic bonding Compounds wherein the residue of the aromatic sulfonic acid contains a hydroxyl group bonded directly to carbon or an ether wherein the H of the OH may be replaced by a substituted or unsubstituted ammonium ion or a Group IA or IIA light metal. www.uspto.gov /go/classification/uspc564/defs564.htm   (2124 words)

Amazon.com: SUBSTITUENT   (Site not responding. Last check: 2007-10-22) Biomimetic synthesis of trans, syn, trans-fused polyoxepanes: Remarkable substituent effects on the endo-regioselective oxacyclization of polyepoxides. Unusual substituent effects in the asymmetric Schmidt reaction of hydroxyalkyl azides and synthetic studies of the marine alkaloid cylindrine C: (Dissertation) by Christopher Ernest Katz (Feb 1, 2006) Some aspects of the sulfur-oxygen bond in organic sulfur groups: An investigation of substituent effects and bonding by means of correlations with physico-chemical... www.amazon.com /s?ie=UTF8&search-alias=aps&keywords=SUBSTITUENT&page=1   (450 words)

ROCO Acid-Base: Substituent effects A substituent is a spectator atom that noticeably perturbs the reactivity of a functional group. Usually, the two compounds are related by replacing the substituent atoms with H, e.g. Therefore, chemists tend to refer to both effects by a single name ("the inductive effect") or by a combined name ("the field-inductive effect") and do not bother trying to distinguish between them. academic.reed.edu /chemistry/roco/AcidBase/substituent.html   (594 words)

[No title] The Cumulative Effect of Substituents and the Solvent Dependence of the Hammett Reaction Constants. Substituent Effects on an Inverse Electron Demand Hetero Diels - Alder Reaction in Aqueous Solution and Organic Solvents: Cycloaddition of Substituted Styrenes to Di(2- pyridyl) - 1,2,4,5 - tetrazine. Substituent Constants for the Empirical Correlation of Electrical Effects. pratt.edu /~mcharton/bio.html   (2537 words)

Dye - Wikipedia, the free encyclopedia However, reduction in alkaline liquor produces the water soluble alkali metal salt of the dye, which, in this leuco form, has an affinity for the textile fibre. Reactive dyes utilize a chromophore containing a substituent that is capable of directly reacting with the fibre substrate. The covalent bonds that attach reactive dye to natural fibers make it among the most permanent of dyes. en.wikipedia.org /wiki/Dye   (1068 words)

ACD/Sigma: Overview   (Site not responding. Last check: 2007-10-22) A common request we receive from researchers and academics is for the actual value of the electronic substituent constant, σ. And in the lab, it will be useful in evaluation of the underlying patterns while choosing a chemical substituent. For any desired substituent, which is attached to the reaction center by a single bond and whose point of attachment is shown with an R-label, the sigma query will be executed at a click of a button. www.acdlabs.com /products/phys_chem_lab/sigma   (204 words)

[No title]   (Site not responding. Last check: 2007-10-22) He thought that, whatever a reaction might be, the rate of it would be affected in about the same way by the same substituent and that you could therefore assign numbers to the substituent effects. Thus, if you could determine a number for the a particular substituent's effect in one reaction, you could use that number to predict the change in rate of another reaction (when that substituent was present) if you knew the rate of reaction of the unsubstituted reactant. Remembering from organic chem that putting a substituent, X, on the ring increases or decreases the acidity of the benzoic acid because of the electron withdrawing or donating nature of the substituent, we can understand where Hammett was headed. wey238ab.ch.iup.edu /olcciii/refine/qsar.htm   (676 words)

Substructure Codes Its substituents are indicated by upper case letters, usually alphabetically. For each substituent, its substituents are, in turn, indicated by lower case letters, usually listed alphabetically. For main groups and their substituents that are part of a ring, the number or upper-case letter is enclosed in parentheses. www.acornnmr.com /NutsHelp/substructure_codes.htm   (596 words)

Organic Nomenclature   (Site not responding. Last check: 2007-10-22) The prefix identifies each of the substituents and gives the location of the substituents and functional group. Give the substituent name a prefix according to the number of identical substitutents present. Preceding the name of each substituent and prefix to substituent, give the number for the substituent followed by a hyphen. www.northland.cc.mn.us /chemistry/organic_nomenclature.htm   (405 words)

Japanese Patent 3718508 B2 - image forming device which is provided with electrophotographic photosensitive material ...   (Site not responding. Last check: 2007-10-22) Ar 4 and Ar5 show alkyl group which may possess heterocyclic group, substituent which may possess hydrogen atom, substituent aryl group, substituent which may be possessed aralkyl group or substituent which may be possessed respectively. Showing, so being m shows aryl group, halogen atom or hydrogen atom which may possess alkoxy group, substituent which may possess alkyl group, substituent which may be possessed that a is substituent dialkyl amino group, substituent which may be possessed integer of 1~6. R2, R 3 and R4 show aralkyl group which may possess aryl group, substituent which may possess hydrogen atom, substituent alkyl group, substituent which may be possessed heterocyclic group or substituent which may be possessed respectively. cxp.paterra.com /jppatent3718508.html   (509 words)

[No title] In contrast, trifluoromethylbenzene is less reactive or deactivated with respect to benzene and directs the new substituent to the meta position. Here is a table that shows the effect of substituents on a benzene ring have on both the rate and orientation of electrophilic aromatic substitution reactions. As a suggested method, look at each of the substituents, label their directing effects, then indicate the sites where they would promote reactivity with small arrows. www.mhhe.com /physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch12substituenteffects.html   (710 words)

enzymes_questions 0.6, the substituent may be considered to be: give the best biological activity (assume only one substituent can be added at the meta position). The substituent should be as large as possible (large, negative E www.pharmacy.umaryland.edu /courses/PHAR531/exams/exam2_98.html   (1143 words)

St to Sy and sigma A dual parameter approach to the correlation analysis of substituent effects, which involves a field constant (F) and a resonance constant (R). Specifically the substituent constant for meta- and for para-substituents in benzene derivatives as defined by Hammett on the basis of the ionization constant of a substituted benzoic acid in water at 25 -constants to the scale of substituent constants which is based on benzoic acid. www.chem.qmul.ac.uk /iupac/gtpoc/StSy.html   (2239 words)

Thiol   (Site not responding. Last check: 2007-10-22) Natural gas distributors began adding various forms of thiols to natural gas, which is naturally odorless, after the deadly 1937 New London School explosion. When a thiol group is a substituent in an alkane, there are several ways of naming the resulting thiol: The preferred method (used by the IUPAC) is to add the suffix -thiol to the name of the alkane. thiol.iqnaut.net   (237 words)

New tertiary constraints between the RNA components of active yeast spliceosomes: A photo-crosslinking study -- RYAN et ... substituent at this position, as the mutation C61U was previously The 5-iodoU54 substituent of U6 was crosslinked to U2 nts 17–19 in gel-purified material (lane 1; asterisks indicate crosslinking-dependent primer extension stops). A primer extension stop due to crosslinking of intron A(+209) (lane 2) was dependent on the 4-thioU substituent of U6 (lane 1; this control was not gel-purified before primer extension). www.rnajournal.org /cgi/content/full/10/8/1251   (8067 words)

Theoretical Studies on Solvent and Substituent Effects of Cuprate Conjugate Addition   (Site not responding. Last check: 2007-10-22) Solvation does not change the mechanism of the conjugate addition but increases the activation energy of the C-C bond-forming step through attenuation of the Lewis acidity of the lithium atoms. The substituent on the enone electrophile was found to have considerable influence on the activation energy. C kinetic isotope effects were found to be susceptible to substituent effects. pubs.acs.org /cgi-bin/abstract.cgi/orgnd7/2001/20/i26/abs/om0105270.html   (169 words)

[No title] Some substituents strengthen acids and weaken bases; other substituents have the opposite effect, the weaken acids and strengthen bases. Substituents exert their effects on acidity or basicity through a combination of resonance and inductive effects. A substituent located meta to the substituent will be affected to a much smaller degree. atom.chem.wwu.edu /kriz/org_18b.ppt   (905 words)

Polymer - Facts, Information, and Encyclopedia Reference article Isotactic chains are defined as having substituent groups aligned in one direction. This enables them to line up close to each other, creating crystalline areas and resulting in highly rigid polymers. Syndiotactic substituent groups alternate regularly in opposite directions. www.startsurfing.com /encyclopedia/p/o/l/Polymer.html   (1363 words)

substituent - OneLook Dictionary Search Tip: Click on the first link on a line below to go directly to a page where "substituent" is defined. Substituent : Drug Discovery and Development [home, info] Phrases that include substituent: aromatic meta substituent, aromatic ortho substituent, substituent electronegativity www.onelook.com /?w=substituent   (205 words)

Ch328_Lec_16 When one attempts to put a second substituent onto an aromatic ring it is found that the first substituent has two effects on this second substitution: The initial substituent has an effect on the reactivity of the aromatic ring. That is some substituents direct additional substituents toward the ortho- and para- positions while others direct toward the meta- position. www.humboldt.edu /~rap1/C328.Su04/C328Notes/C328nLec16.htm   (1125 words)

ACD/Sigma: Key Capabilities ACD/Sigma displays steric constants: molar volume (MV) and molar refractivity (MR) calculated for a fragment of your choice. ACD/Sigma allows you to view the contribution made by each fragment in the substituent toward the entire predicted value. This permits you to make an in-depth analysis of the steric effects, the hydrophobic constant (the π constant of Hansch, enabled in conjunction with ACD/LogP DB calculations), and related phenomena of the various substituents in the molecule of interest. www.acdlabs.com /products/phys_chem_lab/sigma/capabilities.html   (127 words)

Stabilization of the hydrophilic sphere of non-ionic monomers: are all protected in a similar way? -- Violon 74 (888): ... The purpose of this communication is to study the barriers to The three substituent chains on the triiodobenzene ring consist as a second substituent in the tertiary amido group in the two bjr.birjournals.org /cgi/content/full/74/888/1097   (2861 words)

Phenyl as a Substituent This is understood by resonance between the unshared electron pair on nitrogen and the aromatic ring, only possible if the connection is direct, which makes the unshared eleectron pair less available to serve as a base. The resonance possibilities for an aromatic group allow it to serve either as an electron donating substituent when the attached atom needs electrons (carbocation) or as an electron withdrawing substituent when the attached atom has an unshared pair to share (oxygen or nitrogen). There is another reaction which occurs at the atom directly attached to an aromatic ring. chemistry2.csudh.edu /rpendarvis/PhEffects.html   (1361 words)

Supramolecular Chemistry And Self-assembly Special Feature: Substituent effects on cation-pi interactions: A ... at a quantitative level, and it is difficult to predict substituent interaction in complex A plotted as a function of the Hammett substituent constant for the substituent Y (). The corresponding data for edge-to-face aromatic interactions are shown for comparison (14). www.pnas.org /cgi/content/full/99/8/4873   (2050 words)

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