The isomer n-butane can connect in two ways, giving rise to two "-butyl" groups:
If it connects at one of the two terminal carbon atoms, it is normal butyl or n-butyl: CH3−CH2−CH2−CH2− (preferred IUPAC name: butyl)
If it connects at one of the non-terminal (internal) carbon atoms, it is secondary butyl or sec-butyl: CH3−CH2−CH(CH3)− (preferred IUPAC name: butan-2-yl)
The second isomer of butane, isobutane, can also connect in two ways, giving rise to two additional groups:
If it connects at one of the three terminal carbons, it is isobutyl: (CH3)2CH−CH2− (preferred IUPAC name: 2-methylpropyl)
If it connects at the central carbon, it is tertiary butyl, tert-butyl or t-butyl: (CH3)3C− (preferred IUPAC name: tert-butyl)
According to IUPAC nomenclature, "isobutyl", "sec-butyl", and "tert-butyl" used to be allowed retained names. The latest guidance changed that: only tert-butyl is kept as preferred prefix, all other butyl-names are removed. In the convention of skeletal formulas, every line ending and line intersection specifies a carbon atom (unless otherwise indicated) saturated with single-linked hydrogen atoms (unless otherwise indicated). The "R" symbol indicates any radical or other non-specific functional group.
Butyl is the largest substituent for which trivial names are commonly used for all isomers.
The butyl group's carbon that is connected to the rest (R) of the molecule is called the RI or R-prime carbon[citation needed]. The prefixes sec (from "secondary") and tert (from "tertiary") refer to the number of additional side chains (or carbons) connected to the first butyl carbon. The prefix "iso" (from "isomer") means "equal" while the prefix 'n-' stands for "normal".
Butan-2-yl (sec-butyl) group is chiral. The carbon atom at position 2 is a stereocenter. It has four different groups attached: H-, CH3-, CH3-CH2-, and R-. The names of the two chiral groups are: (2S)-butan-2-yl and (2R)-butan-2-yl.
Example
The four isomers (ignoring stereoisomers) of "butyl acetate" demonstrate these four isomeric configurations. Here, the acetate radical appears in each of the positions where the "R" symbol is used in the chart above:
sec-Butyl acetate is chiral, and has one stereocenter, and two enantiomers. The names of enantiomers are:
[(2S)-butan-2-yl] acetate, (+)-sec-Butyl acetate
[(2R)-butan-2-yl] acetate, (-)-sec-Butyl acetate
Therefore, for butyl acetate, the total number of isomers is five, if stereoisomers are included.
Etymology
Alkyl radicals are often considered as a series, a progression sequenced by the number of carbon atoms involved. In that progression, Butyl (containing 4 carbon atoms) is the fourth, and the last with preferred IUPAC name derived from its history. The word "butyl" is derived from butyric acid, a four-carbon carboxylic acid found in rancidbutter.[1] The name "butyric acid" comes from Latinbutyrum, butter. Subsequent preferred IUPAC names for alkyl radicals in the series are simply named from the Greek number that indicates the number of carbon atoms in the group: pentyl, hexyl, heptyl, etc.
tert-Butyl effect
The tert-butyl substituent is very bulky and is used in chemistry for kinetic stabilization, as are other bulky groups such as the related trimethylsilyl group. The effect of the tert-butyl group on the progress of a chemical reaction is called the Thorpe–Ingold effect illustrated in the Diels-Alder reaction below. Compared to a hydrogen substituent, the tert-butyl substituent accelerates the reaction rate by a factor of 240.[2]
^Harper, Douglas. "butane. Dictionary.com". Retrieved 9 Mar 2016.[permanent dead link]
^Factors affecting ease of ring formation. The effect of anchoring substitution on the rate of an intramolecular diels-alder reaction with furan-diene Serge Cauwberghs and Pierre J. De Clercq B. Tinant and J. P. Declercq Tetrahedron Letters Volume 29, Issue 20 , 1988, Pages 2493-2496 doi:10.1016/S0040-4039(00)87916-2
^Wuts, Peter G. M. (2007). Greene's protective groups in organic synthesis (4th ed.). Hoboken, N.J.: Wiley-Interscience. ISBN9780470053485.
^Micheli, Robert A.; Hojos, Zoltan G.; Cohen, Noal; Parrish, David R.; Portland, Louis A.; Sciamanna, Werner; Scott, Melinda A.; Wehrli, Pius A. (March 1975). "Total syntheses of optically active 19-nor steroids. (+)-Estr-4-ene-3,17-dione and (+)-13.beta.-ethylgon-4-ene-3,17-dione". The Journal of Organic Chemistry. 40 (6): 675–681. doi:10.1021/jo00894a003. ISSN 0022-3263.
^"Proceedings of the Chemical Society. July 1961". Proceedings of the Chemical Society (July): 249. 1 January 1961. doi:10.1039/PS9610000229. ISSN 0369-8718.
January 20, 2023
butyl, group, butyl, redirects, here, synthetic, rubber, butyl, rubber, organic, chemistry, butyl, four, carbon, alkyl, radical, substituent, group, with, general, chemical, formula, c4h9, derived, from, either, isomers, butane, isobutane, butane, isomer, buta. Butyl redirects here For the synthetic rubber see Butyl rubber In organic chemistry butyl is a four carbon alkyl radical or substituent group with general chemical formula C4H9 derived from either of the two isomers n butane and isobutane of butane The isomer n butane can connect in two ways giving rise to two butyl groups If it connects at one of the two terminal carbon atoms it is normal butyl or n butyl CH3 CH2 CH2 CH2 preferred IUPAC name butyl If it connects at one of the non terminal internal carbon atoms it is secondary butyl or sec butyl CH3 CH2 CH CH3 preferred IUPAC name butan 2 yl The second isomer of butane isobutane can also connect in two ways giving rise to two additional groups If it connects at one of the three terminal carbons it is isobutyl CH3 2CH CH2 preferred IUPAC name 2 methylpropyl If it connects at the central carbon it is tertiary butyl tert butyl or t butyl CH3 3C preferred IUPAC name tert butyl Contents 1 Nomenclature 2 Example 3 Etymology 4 tert Butyl effect 5 Tert butyl as Protecting group 5 1 Protection amp formation 5 2 Deprotection amp Cleavage 6 ReferencesNomenclature EditAccording to IUPAC nomenclature isobutyl sec butyl and tert butyl used to be allowed retained names The latest guidance changed that only tert butyl is kept as preferred prefix all other butyl names are removed In the convention of skeletal formulas every line ending and line intersection specifies a carbon atom unless otherwise indicated saturated with single linked hydrogen atoms unless otherwise indicated The R symbol indicates any radical or other non specific functional group Skeletal formula Common name PreferredIUPAC name Alternate notation Fully systematic name n butyl butyl butyl butan 1 yl sec butyl butan 2 yl 1 methylpropyl butan 2 yl isobutyl 2 methylpropyl 2 methylpropyl 2 methylpropan 1 yl tert butyl tert butyl 1 1 dimethylethyl 2 methylpropan 2 ylButyl is the largest substituent for which trivial names are commonly used for all isomers The butyl group s carbon that is connected to the rest R of the molecule is called the RI or R prime carbon citation needed The prefixes sec from secondary and tert from tertiary refer to the number of additional side chains or carbons connected to the first butyl carbon The prefix iso from isomer means equal while the prefix n stands for normal Butan 2 yl sec butyl group is chiral The carbon atom at position 2 is a stereocenter It has four different groups attached H CH3 CH3 CH2 and R The names of the two chiral groups are 2S butan 2 yl and 2R butan 2 yl Example EditThe four isomers ignoring stereoisomers of butyl acetate demonstrate these four isomeric configurations Here the acetate radical appears in each of the positions where the R symbol is used in the chart above n butyl acetate sec butyl acetate isobutyl acetate tert butyl acetatesec Butyl acetate is chiral and has one stereocenter and two enantiomers The names of enantiomers are 2S butan 2 yl acetate sec Butyl acetate 2R butan 2 yl acetate sec Butyl acetateTherefore for butyl acetate the total number of isomers is five if stereoisomers are included Etymology EditAlkyl radicals are often considered as a series a progression sequenced by the number of carbon atoms involved In that progression Butyl containing 4 carbon atoms is the fourth and the last with preferred IUPAC name derived from its history The word butyl is derived from butyric acid a four carbon carboxylic acid found in rancid butter 1 The name butyric acid comes from Latin butyrum butter Subsequent preferred IUPAC names for alkyl radicals in the series are simply named from the Greek number that indicates the number of carbon atoms in the group pentyl hexyl heptyl etc tert Butyl effect EditThe tert butyl substituent is very bulky and is used in chemistry for kinetic stabilization as are other bulky groups such as the related trimethylsilyl group The effect of the tert butyl group on the progress of a chemical reaction is called the Thorpe Ingold effect illustrated in the Diels Alder reaction below Compared to a hydrogen substituent the tert butyl substituent accelerates the reaction rate by a factor of 240 2 The tert butyl effect is an example of steric hindrance Tert butyl as Protecting group EditTert butyl tBu ether is an acid labile protecting group for alcohols 3 Protection amp formation Edit A traditional way to introduce tBu group to hydroxyl group is by treating the compound with isobutylene in the presence of Bronsted acid or Lewis acid 4 5 Deprotection amp Cleavage EditReferences Edit Harper Douglas butane Dictionary com Retrieved 9 Mar 2016 permanent dead link Factors affecting ease of ring formation The effect of anchoring substitution on the rate of an intramolecular diels alder reaction with furan diene Serge Cauwberghs and Pierre J De Clercq B Tinant and J P Declercq Tetrahedron Letters Volume 29 Issue 20 1988 Pages 2493 2496 doi 10 1016 S0040 4039 00 87916 2 Wuts Peter G M 2007 Greene s protective groups in organic synthesis 4th ed Hoboken N J Wiley Interscience ISBN 9780470053485 Micheli Robert A Hojos Zoltan G Cohen Noal Parrish David R Portland Louis A Sciamanna Werner Scott Melinda A Wehrli Pius A March 1975 Total syntheses of optically active 19 nor steroids Estr 4 ene 3 17 dione and 13 beta ethylgon 4 ene 3 17 dione The Journal of Organic Chemistry 40 6 675 681 doi 10 1021 jo00894a003 ISSN 0022 3263 Proceedings of the Chemical Society July 1961 Proceedings of the Chemical Society July 249 1 January 1961 doi 10 1039 PS9610000229 ISSN 0369 8718 Retrieved from https en wikipedia org w index php title Butyl group amp oldid 1127099252, wikipedia, wiki, book, books, library,
