Abstract: A method for producing a polymerizable composition, the method including: step (1) of preparing composition A having a water content of 200 ppm by mass or less, the composition A including a polyisocyanate component but not including a polymerization catalyst; step (2) of preparing composition B having a water content of 1,000 ppm by mass or less, the composition B including a polythiol component; and step (3) of mixing the composition A and the composition B and obtaining a polymerizable composition, and also a method for producing an optical component, the method including: a step of injecting the above-mentioned polymerizable composition into a molding die; and a step of polymerizing the polymerizable composition.

Abstract: Disclosed are cross-linked polymers comprising a monomer, a cross-linker, and a sulfur moiety in the polymer backbone. Methods of making cross-linked polymers comprising a monomer, a cross-linker, and a sulfur moieity in the polymer backbone are disclosed. A metal complex, comprising a cross-linked polymer chelated to a toxic heavy metal atom or ion is disclosed. The disclosure provides a method of toxic heavy metal remediation using the cross-linked polymers. Also provided are articles and coatings comprising the disclosed cross-linked polymers.

Abstract: The present invention relates to novel methods for preparing a polythiol compound for use in an optical material and polymerizable compositions including a polythiol compound prepared by the methods. According to the methods, a polythiol compound with uniform color, high purity and high quality can be prepared at reduced cost. The polymerizable compositions can be used to manufacture clear, transparent optical lenses with good heat resistance and excellent optical properties.

Abstract: Provided is a method for producing a polythiol compound, comprising: a step for reacting 2-mercaptoethanol with a defined epihalohydrin compound at a temperature of 10° C. to 50° C. to obtain a defined polyalcohol compound; a step for reacting the polyalcohol compound thus obtained with thiourea in the presence of hydrogen chloride to obtain an isothiuronium salt; a step for adding, while maintaining a reaction solution containing the isothiuronium salt thus obtained at a temperature of 15° C. to 60° C., aqueous ammonia to the reaction solution within 80 minutes, thereby hydrolyzing the isothiuronium salt to obtain a defined polythiol compound; and a step for adding hydrochloric acid which is a concentration of 25% to 36% to the solution containing the polythiol compound thus obtained, washing the solution at a temperature of 10° C. to 50° C. to purify the polythiol compound.

Abstract: Provided is a method for producing a polythiol compound, comprising: a step for reacting a polyalcohol compound represented by the following formula (4) with thiourea in the presence of hydrogen chloride to obtain an isothiuronium salt; a step for adding, while maintaining a reaction solution containing the isothiuronium salt thus obtained at a temperature of 20° C. to 60° C., aqueous ammonia to the reaction solution within 80 minutes, thereby hydrolyzing the isothiuronium salt to obtain a polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae (6) to (8); and a step for adding hydrochloric acid which is a concentration of 30% to 36% to the solution containing the polythiol compound thus obtained, washing the solution at a temperature of 30° C. to 55° C. to purify the polythiol compound.

Abstract: The present invention relates to a polythiol compound for a high quality optical material that exhibits excellent physical properties in terms of color, a composition for an optical material including the polythiol compound, a method for producing an optical material, and a method for preparing the polythiol compound. The method includes reacting an epichlorohydrin compound containing 0.5% by weight or less of impurities with 2-mercaptoethanol. The polythiol compound is prevented from being colored. The polythiol compound can be used to produce a urethane optical material that is prevented from being colored and has a low yellowness index and a good color. The polythiol compound can be used to produce various optical materials including urethane optical materials. The optical material can be used to manufacture an optical lens having a good color. The optical lens can be used as a spectacle lens, a polarizing lens, a camera lens, or the like.

Abstract: A composition that includes one or more compounds represented by the formula (R1)a(X)(R2)b wherein R1 and R2 are the same or different and are the residue of an alkyl group having from 4 to 40 carbon atoms, X is the residue of an aliphatic polythiol, aromatic polythiol, cycloaliphatic polythiol, ester or acid containing thiol, or ester or acid containing polythiol, a is a value from 1 to 6, and b is a value from 0 to 6. The composition has a viscosity (Kv100) from 2 to 30 at 100° C., a viscosity index (VI) from 100 to 200, and a Noack volatility of no greater than 20 percent. The disclosure also relates to a process for producing the composition, a lubricating oil base stock and lubricating oil containing the composition, and a method thr improving one or more of solubility and dispersancy of polar additives in a lubricating oil by using as the lubricating oil a formulated oil containing the composition.

Abstract: The purpose of the present invention is to provide a printed circuit board wherein a resin layer exhibits excellent adhesion and a method for manufacturing said printed circuit board. This printed circuit board is provided with an insulating substrate, metal wiring laid out on said insulating substrate, and an insulating layer disposed on top of said metal wiring. A layer consisting of a thiol compound having at least four functional groups represented by formula (1) is interposed between the metal wiring and the insulating layer at the interface therebetween.

Abstract: Provided are a novel heterocyclic compound represented by formula (1), and a field-effect transistor having a semiconductor layer comprising the aforementioned compound. Also provided is a method for producing an intermediate enabling the production of the aforementioned novel heterocyclic compound. (In the formula, R1 and R2 represent a hydrogen atom, a C2-16 alkyl group or an aryl group. However, when R1 each independently represents a C2-16 alkyl group or an aryl group, R2 represents a hydrogen atom or each independently represents an aryl group; and when R1 represents a hydrogen atom, R2 each independently represents an aryl group.

Abstract: The present invention provides a diacetylene derivative represented by the following formula (A) which exhibits liquid crystallinity by itself and has a large refractive index anisotropy or does not exhibit liquid crystallinity by itself but exhibits a large refractive index anisotropy when added to a liquid crystalline compound: R1-Sp1-(Ar1)p-(Ar3)q-(Phe)r-C?C—C?C-(Phe)r-(Ar4)q-(Ar2)p-Sp2-R2??(A) (wherein R1 and R2 are a hydrogen, halogen, cyano, isothiocyanate, alkyl, alkenyl, alkynyl or reactive group, SP1 and SP2 are each a spacer group, Ar1 and Ar2 are each a non-substituted or substituted aromatic carbocyclic or heterocyclic group, Ar3 and Ar4 are each a non-substituted or substituted heterocyclic group, Phe is a non-substituted or substituted 1,4-phenylene group, and p, q and r are each 0 or 1.

Abstract: The present disclosure relates to a new polymerization process in which ethylenically unsaturated monomers are polymerised by a living radical polymerization process in the presence of an initiator and a catalyst. Polymers produced by this new process are also thought to be novel and may be used to derivatise biological molecules to improve their efficacy as therapeutic treatments. A preferred polymer is of formula The polymers are particularly suitable for derivatising proteins, such as interferon-?.

Abstract: Compounds of the formula (I), wherein X is a single bond, CRaRb O, S, NRC, NCORC, CO, SO or SO2; L, L1, L2, L3, L4, L5, L6, L7 and L8 are for example hydrogen, R1 or COT; T denotes T1 or O-T2; T1 and T2 for example are hydrogen, C1-C20alkyl, C3-C12cycloalkyl, C2-C20alkenyl, C5-C12cycloalkenyl, C6-C14aryl, C3-C12heteroaryl, C1-C20alkyl substituted by one or more D, C2-C20alkyl interrupted by one or more E, C2-C20alkyl substituted by one or more D and interrupted by one or more E or Q; R1, R2, R3, R4, Ra, Rb and Rc are T1; D is for example R5, OR5, SR5 or Q1; E is for example O, S, COO or Q2; R5 and R6 for example are hydrogen, C1-C12alkyl or phenyl; Q is for example C6-C12bicycloalkyl, C6-C12bicycloalkenyl or C6-C12tricycloalkyl; Q1 is for example, C6-C14aryl or C3-C12heteroaryl; Q2 is for example C6-C14arylene or C3-C12heteroarylene; Y is an anion; and M is a cation; provided that at least one of L, L1, L2, L3, L4, L5, L6, L7 and L8 is other than hydrogen; and provided that (i) at least one of T1 or T2 is a g

Abstract: The present invention is directed towards a new class of semi-conducting acene derivatives. These compounds are all soluble species and they all possess superior resistance to photooxidation as compared to their counterparts that lack the substitution patterns disclosed herein.

Abstract: Disclosed are thioethers, methods for preparing such thioethers, and curable compositions, such as coating and sealant compositions, that include such thioethers. The thioethers can be the reaction product of (a) an alpha, omega dihalo organic compound, (b) a metal hydrosulfide, and (c) a metal hydroxide.

Abstract: Disclosed are thioethers, methods for preparing such thioethers, and curable compositions, such as coating and sealant compositions, that include such thioethers. The thioethers can be the reaction product of (a) an alpha, omega dihalo organic compound, (b) a metal hydrosulfide and (c) a metal hydroxide.

Abstract: Dental compositions and disulfide monomers are described. The disulfide monomer comprise a disulfide backbone group wherein each of the sulfur atoms are bonded to an ethylenically unsaturated group via a divalent linking group and the linking group comprises at least one heteroatom; and at least one other monomer ethylenically unsaturated monomer.

Abstract: Dental compositions and disulfide monomers described. The disulfide monomer comprises a disulfide backbone group wherein each of the sulfur atoms are bonded to a group terminating with an ethylenically unsaturated norbornyl group; and at least one other monomer comprising at least two ethylenically unsaturated groups.

Abstract: Dental compositions and disulfide monomers described. The disulfide monomer comprises a disulfide backbone group wherein each of the sulfur atoms are bonded to a group terminating with an ethylenically unsaturated norbornyl group; and at least one other monomer comprising at least two ethylenically unsaturated groups.

Abstract: Compounds of the formula (I), L, L?, L?, L1, L?1, L?1, L2, L?2, L?2, L3, L?3, L?3, L4, L?4, L?4, L5, L?5, L?5, L6, L?6, L?6, L7, L?7, L?7, L8, L?8 and L?8 independently of one another are hydrogen or an organic substituent; and/or one or more of the pairs L3 and L5, L?3 and L?5 or L?3 and L?5 together denote a single bond, provided that the respective X, X? or X? is not a single bond; and/or L3 and L5, L?3 and L?5 or L?3 and L?5 together denote an organic linking group; and/or one or more of the pairs L1 and L3, L1 and L, L5 and L7, L?1 and L?3, L?1 and L?, L?5 and L?7, L?1 and L?3, L?1 and L?, or L?5 and L?7, together denote an organic linking group; provided that at least one of L, L?, L?, L1, L?1, L?1, L2, L?2, L?2, L3, L?3, L?3, L4, L?4, L?4, L5, L?5, L?5, L6, L?6, L?6, L7, L?7, L?7, L8, L?8 and L?8 is other than hydrogen; X, X? and X? independently of one another are a single bond, CRaRb O, S, NRc or NCORc; Ra, Rb and Rc independently of one another are hydrogen or an organic substituent; and Y is an ino

Abstract: Disclosed is a process for producing effectively a high performance optical material (e.g. a lens) made of a polyurethane resin, which is transparent and colorless without a strain. In this process, the optical material is produced without causing striation or clouding by polymerizing a polymerizable composition comprising a polythiol compound and a polyiso(thio)cyanate compound, and characterized in that a water content in the composition is 10 to 300 ppm.

Abstract: A compound for an organic thin film transistor having a structure of the following formula (1): wherein R1 to R6 are independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 30 carbon atoms, a haloalkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, a haloalkoxy group having 1 to 30 carbon atoms, an alkylthio group having 1 to 30 carbon atoms, a haloalkylthio group having 1 to 30 carbon atoms, an alkylamino group having 1 to 30 carbon atoms, a dialkylamino group having 2 to 60 carbon atoms (the alkyl groups may be combined with each other to form a ring structure containing the nitrogen atom), an alkylsulfonyl group having 1 to 30 carbon atoms, a haloalkylsulfonyl group having 1 to 30 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, an aromatic heterocyclic group having 3 to 60 carbon atoms, an alkylsilyl group having 3 to 20 carbon atoms, an alkylsilylacetylene group having 5 to 60 carbon atoms or a cyano group, which each may have

Abstract: Provided is a process for producing a polythiol compound for an optical material, the method includes reacting 2-mercaptoethanol with an epihalohydrin compound to give polyalcohol, and preparing a polythiol compound through the polyalcohol, wherein a content of bis(2-hydroxyethyl)disulfide in the 2-mercaptoethanol is 0.5 wt % or less.

Abstract: A process for producing a (poly)thiol compound for an optical material. The process involves reacting an organic (poly)halogen compound or a (poly)alcohol compound with thiourea to produce an isothiuronium salt and hydrolyzing the isothiuronium salt in the presence of ammonia water to thereby produce the (poly)thiol compound, wherein the thiourea has a calcium content of not more than 1.0 wt %.

Abstract: The present invention is directed towards a new class of semi-conducting acene derivatives. These compounds are all soluble species and they all possess superior resistance to photooxidation as compared to their counterparts that lack the substitution patterns disclosed herein.

Abstract: The present invention is directed towards a new class of semi-conducting nonacene derivatives. These compounds are all soluble species and they all possess superior resistance to oxidation as compared to their counterparts that lack the substitution patterns disclosed herein.

Abstract: Disclosed are thioethers, methods for preparing such thioethers, and curable compositions, such as coating and sealant compositions, that include such thioethers. The thioethers can be the reaction product of (a) an alpha, omega dihalo organic compound, (b) a metal hydrosulfide, and (c) a metal hydroxide.

Abstract: Provided is a process for producing a polythiol compound for an optical material, the method includes reacting 2-mercaptoethanol with an epihalohydrin compound to give polyalcohol, and preparing a polythiol compound through the polyalcohol, wherein a content of bis(2-hydroxyethyl)disulfide in the 2-mercaptoethanol is 0.5 wt % or less.

Abstract: Disclosed are thioethers, methods for preparing such thioethers, and curable compositions, such as coating and sealant compositions, that include such thioethers. The thioethers can be the reaction product of (a) an alpha, omega dihalo organic compound, (b) a metal hydrosulfide and (c) a metal hydroxide.

Abstract: Benzophenone/thioxanthone derivatives useful as photoinitiators are provided as well as photopolymerizable compositions comprising the benzophenone/thioxanthone derivatives.

Abstract: Provided is a process for producing a polythiol compound for an optical material, the method includes reacting 2-mercaptoethanol with an epihalohydrin compound to give polyalcohol, and preparing a polythiol compound through the polyalcohol, wherein a content of bis(2-hydroxyethyl) disulfide in the 2-mercaptoethanol is 0.5 wt % or less.

Abstract: The present invention relates to the improvement of organic electronic devices, in particular electroluminescent devices, by using compounds which can have a plurality of isomers, where one of these isomers is present in excess.

Abstract: A compound having thioacetal skeleton, a precursor thereof, a cured product thereof, and a composition for their production are provided for the thermally dissociatable material based on the inventors' finding that a thioacetal group is thermally dissociatable. The use of the thermally dissociatable material of the invention enables softening or liquefaction at any desired timing through thermal dissociation at a temperature below the thermal decomposition temperature of the cured product. It is thus possible to disassemble the structure to which the thermally dissociatable material had been attached in a short time. The thermally dissociatable material is useful as a highly disposable plastic material and is adapted for use as a sealant, coating composition or adhesive. Such material may be used, for example, as a curing agent for urethane curable composition or epoxy curable composition, or as a self-curable material.

Abstract: A process for reacting a first component with itself or a second component to produce a third component in which a first material comprising a first component or said first component and a second component is fed to divided wall column having a catalytic distillation structure in at least one of the separate vertical sections of the divided wall column where concurrently: (1) a first component alone or with a second component is contacted with a catalytic distillation structure in a distillation reaction zone thereby catalytically reacting at least a portion of the first component with itself or with the second component to form a product and (2) a first mixture comprising the first component and the product or the first component, the second component and the product; and withdrawing the product from the distillation column reactor; while within the column concurrently with the catalytic reaction and fractionation a second mixture is fractionated, which contains the first component and the product or first a

Abstract: A composition containing 3,3?-thiobis(propane-1,2-dithiol) and one or more enic compounds which composition is photocurable and can give a cured product having a high refractive index and adequate hardness.

Abstract: A process for reacting a first component with itself or a second component to produce a third component in which a first material comprising a first component or said first component and a second component is fed to divided wall column having a catalytic distillation structure in at least one of the separate vertical sections of the divided wall column where concurrently: (1) a first component alone or with a second component is contacted with a catalytic distillation structure in a distillation reaction zone thereby catalytically reacting at least a portion of the first component with itself or with the second component to form a product and (2) a first mixture comprising the first component and the product or the first component, the second component and the product; and withdrawing the product from the distillation column reactor; while within the column concurrently with the catalytic reaction and fractionation a second mixture is fractionated, which contains the first component and the product or first a

Abstract: The invention relates to bis(alkylthio)carbenium salts of the formula I with the stated definitions for R1, R2, R3 and Y?, and to a process for the preparation thereof. The compounds according to the invention are advantageously suitable as electrophilic reagents for the transfer of fluorinated alkyl and acyl radicals onto nucleophilic compounds.

Abstract: The continuous process for manufacturing bisphenol A according to the invention, by reacting phenol and acetone in the presence of a strong acid catalyst and a co-catalyst, is carried out using as co-catalyst a dithio ether of general formula: 1

Abstract: The invention aims at providing novel sulfur compounds, molecular compounds containing the same as the component compound, and so on. The above aim is achieved by using sulfur compounds of the general formula (I) wherein Rs are each independently hydrogen, optionally substituted C1-6 alkyl, optionally substituted C2-6 alkenyl, optionally substituted aryl, chloro, or bromo; m is an integer of 0, 1, or 2; and Z is a group represented by any of the general formulae (II) to (V) (wherein R and m are each as defined above; W is hydrogen or C1-6 alkyl; and Y is a direct bond, C1-3 alkylene, or phenylene).

Abstract: The present invention is directed to labeled compounds, [2-13C]dithiane wherein the 13C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-13C]dithiane wherein the 13C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [2H1−2, 13C]methanol (arylthio)-, acetates wherein the 13C atom is directly bonded to exactly one or two deuterium atoms.

Abstract: A process for the manufacture of a polyphenol compound such as bisphenol-A by introducing into a reaction zone a phenolic compound reactant, a carbonyl compound reactant, and a catalyst promoter comprising a dithioketal compound, and reacting the ingredients within the reaction zone in the presence of an acid catalyst.

Abstract: A process for purifying alkenyl compounds having a divalent or trivalent heteroatom in the &agr;-position relative to the double bond by distillation comprises carrying out at least two distillations in which the purified alkenyl compounds are obtained from the gas phase by condensation, where the time between the first distillation after the synthesis of the alkenyl compounds and at least one further distillation is at least one day and the purified alkenyl compounds have an APHA color number of <30.

Abstract: A new method for producing unsymmetrically substituted fluorenyl compounds, one step of which is the preparation of 2,7-disubstituted fluoren-9-one derivatives via the nucleophilic substitution of a compound of the formula D wherein A′ is selected from the group consisting of —Br, —Cl, —F, —NO2, and —CN; A is selected from the group consisting of —NO2, —CN, —CO2R, —C(O)R, —SO2R, —SO2RF, —C(CN)═C(CN)2 and —CH═C(CN)2; RF is —CpF2p+1, p=from about 0 to about 10; R is an straight, branched or cyclic aliphatic alkyl group having about 1 to 10 carbon atoms, or an aromatic group such as phenyl or naphthyl; and is a carbonyl or a protected carbonyl such as a ketal or thio-ketal such as wherein R′ is —CrH2r+1; R″ is —(CH2)r—; and r is independently 2 or 3, with a nucleophilic reagent in the presence of an aprotic solvent

Abstract: Presulfurizing process and presulfurization promoter for a desulfurization catalyst to be used in a hydrodesulfurization unit of petroleum refinery of high molecular hydrocarbons, in which fresh metal oxide in said desulfurization catalyst is sulfurized with hydrogen sulfide produced from sulfur-containing compounds in a feed stream. In the invention, a compound having mercapto alkylthio group: HS—CmH2m—S— (in which “m” is an integer of 2 to 4) is added as promoter at a proportion of 10 ppm to 0.5% by weight and presulfurization is promoted at 180 to 260° C.

Abstract: The invention provides a complexant compound of formula IR.sup.3 S (CR.sup.1.sub.2).sub.n N(R.sup.2).sub.i (CR.sup.1.sub.2).sub.n X(CR.sup.1.sub.2).sub.n N(R.sup.2).sub.i (CR.sup.1.sub.2).sub.n SR.sup.3(I )(wherein each n, which may be the same or different, is an integer 2, 3 or 4 (preferably 2); each i, which may be the same or different, represents 0 or 1; each R.sup.3, which may be the same or different, is H or a thiol protecting group, preferably a protecting group; X is O, S, N, NR.sup.4 or a substituted phosphorus (eg. oxo substituted phosphorus), preferably S or N; each R.sup.4, which may be the same or different, is hydrogen or an optionally substituted organic group; each R.sup.1, which may be the same or different, is hydrogen or an optionally substituted organic group, or a moiety CR.sup.1.sub.2 may represents a carbonyl group or two, three or four R.sup.

Abstract: This invention relates to new bifunctional chelating agents with intermittent chalcogen atoms, pharmaceuticals containing these compounds, their use in radiodiagnostics and radiotherapy, and methods for the production of these compounds.The compound according to the invention has the general formula (I)M--Lwhere M represents a radionuclide and L a ligand of the general formula (II).It was found, surprisingly, that these new, bifunctional chelating agents with intermittent chalcogen atoms and their coupling products with compounds that accumulate specifically are excellently suited for producing radiopharmaceuticals for diagnostic and therapeutic purposes.

Abstract: Ligands for radiopharmaceutical use are capable of chelating radiometal species and of being bound to biological targeting molecules. The ligands have the formula (a) and (b), where A, A'=--SZ or Y, B=O or S, Y=(c), Z=H or a thiol protecting group, m=2 or 3, n=2 or 3, q=0 or 1, R=H or unsubstituted or substituted hydrocarbon and pharmaceutically acceptable salts, provided that at least one CR.sub.2 group represents CO and forms, together with an adjacent N atom; a --CONR-- amide group.

Abstract: An object is to provide a method for the production of a sulfide group-containing thiol compound which comprises using a solvent capable of effecting the ring-opening addition reaction of an alkylene sulfide to a thiol compound without inducing the alkylene sulfide to polymerize. A method for the production of a sulfide group-containing thiol compound, which comprises effecting the ring-opening addition reaction of an alkylene sulfide represented by the general formula (1): ##STR1## (wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4, which may be identical or different, stand for a hydrogen atom, an alkyl group of 1 to 10 carbon atoms, or an aromatic group of 6 to 15 carbon atoms) to a thiol compound in a solvent of an amide compound or urea substituent-containing compound.

Abstract: A novel sulfur-containing compound represented by the general formula (I): ##STR1## wherein n is an integer from 0 to 2; R represents a hydrogen atom, a vinyl group, a methacryloyl group, a vinylbenzyl group, a glycidyl group, an acryloyl group or an allyl group; and the case where n is 0 and R is a hydrogen atom is excluded, and a method for preparing said sulfur-containing compound. The novel sulfur-containing compound of the present invention can be copolymerized with various copolymerizable compounds to yield excellent hardened products of high refractive index. The novel sulfur-containing compound of the present invention can therefore be used as a very useful monomer for the production of optical materials, paints, adhesives, sealants, etc. having excellent properties.

Abstract: A process which can be used to produce an aromatic sulfide compound having the formula of (R.sub.4-n)(X.sub.n)(W)Ar--S--R' is provided. The process comprises contacting, in the presence of a surfactant, a halo-substituted aromatic compound in an aqueous solution with a salt of a mercaptan under conditions sufficient to produce the aromatic sulfide in which the halo-substituted aromatic compound and salt of mercaptan are each present in an amount effective to synthesize the aromatic sulfide wherein R is hydrogen or a hydrocarbyl radical, X is a halogen, n is a number from 0 to 3, W is a substituent, Ar is an aromatic ring, and R' is a hydrocarbyl radical.

Abstract: The present invention provides an ozonide reducing agent for use in the ozonolysis reaction of an organic compound, the ozonide reducing agent finding wide applications, and being safe and inexpensive from a commercial viewpoint and easy to treat for disposal.The ozonide reducing agent of the invention is a compound wherein sulfur has, at both ends of its molecule, a hydrocarbon residue substituted by a polar functional group.