Groups alkyl

Alkyl groups are groups which lack one hydrogen atom compared to its parent alkane. For example, methyl group is CH3—, which lacks one hydrogen atom with respect to its parent alkane, methane (CH ). Similarly, ethyl group (CjHj—lacks one hydrogen atom compared to ethane 

Main rules and strategies for the lUPAC naming of alkanes 

Write out the expanded structural formula, if it is not given in the expanded form. 

Find the longest carbon chain and then identify the alkyl or other substituents that are connected to this long chain. 

The numbering of carbons should start from the specific end of the long chain, so that the numbers assigned for the substituents are the lowest. 

Alkane Name Alkyl group Name (abbreviation) 

CHAPTER 3 ORGANIC COMPOUNDS ALKANES AND THEIR STEREOCHEMISTRY 

FIGURE 3.3 Alkyl groups generated from straight-chain alkanes. 

Tertiary carbon (3°) is bonded to three other carbons. 

Quaternary carbon (4°) is bonded to four other carbons. 

TABLE 3.4 Some Straight-Chain Alkyl Croups 

Generation of straight-chain and branched-chain alkyl groups from n-alkanes. 

The method of naming alkyl groups described in this section is permitted by the 1979, 1993, and 2004 versions of the lUPAC rules. 

An alkyl group lacks one of the hydrogens of an alkane. A methyl group (—CH3) is an alkyl group derived from methane (CH4). Unbranched alkyl groups in which the point of attachment is at the end of the chain are named in lUPAC nomenclature by replacing the -ane endings of Table 2.2 by -yL 

The dash at the end of the chain represents a potential point of attachment for some other atom or group. 

Carbon atoms are classified according to their degree of substitution by other carbons. A primary carbon is directly attached to one other carbon. Similarly, a secondary carbon is directly attached to two other carbons, a tertiary carbon to three, and a quaternary carbon to four. Alkyl groups are designated as primary, secondary, or tertiary according to the degree of substitution of the carbon at the potential point of attachment. 

Ethyl (CH3CH2—), heptyl [CH3(CH2)5CH2—], and octadecyl [CH3(CH2)i6CH2—] are examples of primary alkyl groups. 

Fused pyrazole compounds have been prepared from A -alkyl-substituted pyrazoles. For example, a palladium-catalyzed/norbornene-mediated sequential coupling reaction involving an aromatic sp C-H functionalization as the key step has been described, in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one pot. A variety of highly substituted six-membered annulated pyrazoles 433 were synthesized in a one-step process in moderate yields from iV-bromoalkyl pyrazoles 431 and aryl iodides 432 (Equation 87) 20060L2043 . An intramolecular cyclization version has also been reported. Exposure of 2equiv of -butyllithium to l//-pyrazole-l-alkanoic acids 434 afforded the cyclic ketones 435 via a Parham-type cyclization process (Equation 88) 1997SL1013 . 

A series of 2-(5-aryl-3-styryM,5-dihydro-l//-pyrazol-l-yl)-4-(trifluoromethyl)pyrimidines 453 were synthesized by the cyclocondensation of5-aryl-l-carboxamidino-3-styryl-4,5-dihydro-l//-pyrazoles 451 with 4-alkoxy-1,1,1-trifluoro-alk-3-en-2-ones 452 (Equation 91) 2006S2349 . 

Sequential functionalization of pyrazole-l-oxides via regioselective metallation led to the synthesis of 3,4,5-trisub-stituted-l-hydroxypyrazoles 2002JOC3904 . 3-Acylated-2-(4-methoxybenzyl)-2//-pyrazole 1-oxides were formed by the reaction between a 3-magnesium 2//-pyrazole-l-oxide and acid chlorides 2002J(P1)428 . 3-Arylated-l-hydroxypyrazoles were synthesized from 3-metallated-pyrazole 1-oxides 2001JOC8654 . The reaction between hexafluorobenzene and the anion of 1-hydroxypyrazole affords a mixture of the products of bis-, tetrakis-, and hexakis-substitution 2004ARK100 . In the case of hexakis(bromomethyl)benzene, its reaction with 1-hydroxy-pyrazole leads to the hexakis-substituted product. 

Electrochemical reduction and chemical reduction by cysteine or potassium ferrocyanide of iV-nitropyrazoles provided a new source of nitric oxide 1996MC11 . 

7 Reactivity of Substituents Attached to Ring Carbons 8.01.7.1 Alkyl Groups 

R = 4-MeC6H4, 4-PhCsH4, 4-MeOCeH4, 4-FC6H4, 1-naphthyl, 2-naphthyl, 9-anthryl 

Branched alkyl groups are named by using the longest continuous chain that begins at the point of attachment as the parent. Thus, the systematic names of the two C3H7 alkyl groups are propyl and 1-methylethyl. Both are better known by their common names, n-propyl and isopropyl, respectively. 

If one hydrogen is removed from an alkane, an alkyl group is formed. The general formula for an a%l group is C H2r,+ i. Instead of the -ane suffix in alkanes, -yl is used for naming alkyl groups. They can also be shown by R . R represents radical . 

A carbon atom in an alkane can be named as primary, secondary or tertiary according to the number of other carbon atoms to which it is attached. 

Alkyl groups can be defined as primary, secondary or tertiary depending upon their structures. 

ICIPAC The International Union of Pure and Applied Chemistry. 

Propose structures that meet the following descriptions  

How many isomers are there with the following descriptions  

Methane A methyl group Methyl alcohol (methanol) Methylamine 

4 he symbol R is used in organic chemistry to represent a organic 

Propose structures that meet tlie following descriptions  

When trying to prepare the 4-chloro derivative of l-adamantyl-3,5-dimethylpyrazole (179 Ad = 

Transformation of 4-methylpyrazoles into 4-carboxylic acids takes place readily by cobalt-manganese bromide mediated oxidation 91CL585 . Begtrup 92JCS(P1)2555 has developed a method to activate methyl groups at positions 3 and 5 using 2-alkoxy-pyrazohum derivatives (181) in this way pyrazoles (182) were prepared (X = D, I, OMe). 

Nitration at the para position of C-phenylpyrazoles has been already reported (see Section 

SAMPLE SOLUTION (a) There are two C4H10 isomers. Butane (see Table 2.4) is the lUPAC name for the isomer that has an unbranched carbon chain. The other isomer has three carbons in its longest continuous chain with a methyl branch at the central carbon its lUPAC name is 2-methylpropane. 

So far, the only branched aUcanes that we ve named have methyl groups attached to the main chain. What about groups other than CH3 What do we call these groups, and how do we name alkanes that contain them  

The reactivity of pyridazine and pyridazine iV-oxide methyl substituents is reviewed in CHEC-I 84CHEC-l(3B)l . In particular, susceptibility to oxidation to the aldehydes or acids, condensation with aldehydes, and reactions of lithiated intermediates are discussed for instance, treatment of 3-methylpyridazine-1 -oxide with acetic anhydride gives, after hydrolysis, 3-hydroxymethylpy ridazine. 

Free radical chlorination of 4-t-butyl-3,6-dichloropyridazine with sulfuryl chloride gives 4-(2-chloro-l,l-dimethylethyl)-3,6-dichloropyridazine as the major product, but only when the reaction is stopped after about 20% conversion. Further reaction results in random chlorination of the t-butyl group and the 4-(2-chloro-1,1-dimethylethy 1) product is better made from the corresponding alcohol 88JOC5704 . 

Primary carbon (1 ) Secondary carbon (2°) is bonded to one is bonded to two 

The terms primary, secondary, tertiary, and quaternary are routinely used in organic chemistry, and their meanings need to become second nature. For example, if we were to say, Citric acid is a tertiary alcohol, we would mean that it has an alcohol functional group (-OH) bonded to a carbon atom that is itself bonded to three other carbons. (These other carbons may in turn cormect to other functional groups.) 

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Either by alkyl groups which are designated by the letter R, which is equivalent to to give alkyl-aromatics. The prefixes ortho, meta... 

Some of the common aromatics found in crude oil are the simple derivatives of benzene in which one or more alkyl groups (CHg) are attached to the basic benzene molecule as a side chain which takes the place of a hydrogen atom. These arenes are either liquids or solids under standard conditions. 

The species at the centre of tire rings is usually Si or Ge and tire bridging atom is oxygen. In one study tire peripheral hydrogens on tire phtlialocyanine molecules were replaced by alkyl groups and tire resulting polymers could be rendered soluble in ordinary organic solvents [108, 109 and 110]. Successful deposition of several of tliese materials has been achieved and different techniques were employed to study tlieir stmctural properties [109, ill, ill, ill and 1141. 

In silicon tetrachloride, SiC, chlorine atoms can be replaced by methyl or other alkyl groups to give, for example, CHjSiClj and (CH3)2SiCl2. These two compounds are obtained when methyl... 

Thus, the values calculated for effective polarizability at the nitrogen atom for a series of 49 amines carrying only alkyl groups was correlated directly with their proton affinities, a reaction that introduces a positive charge on the nitrogen atom by protonation (Figure 7-7) [40. ... 

The half-lives for these four compounds taken from the literature allowed the estimation of the Four reaction rates necessai to model their degradation [18], As a first approximation, the rate of hydrolysis of the C-Cl bond of all Four, -triazine compounds was assumed to be the same and to be 5.0 x 10 s on the basis of literature precedence. This approximation seems reasonable as the four structures differ only in the alkyl groups at a site quite remote from the C-CI bond. Furthermore, among the Four reaction steps hydrolysis is the slowest anyway. 

The removal of the two alkyl groups comprises the two primai y steps, the abstraction of the ethyl group being the dominant one. These products show up first, as can be seen on the left-hand side of Figure 10.3-14, It can also be seen that it is expected that after one year an apprceiable amount of s-triazine eom-pounds will still be found in the soil. 

If, however, a tertiary amine has two alkyl groups and also an aryl group having the para position unsubstituted, then the action of nitrous acid is to insert the nitroso group directly into this para position. Dimethylaniline, for example, when treated with nitrous acid readily gives p-nitrosodimethyl-... 

Esters of one alcohol should not normally be recrystallised from another alcohol. In the above case, however, no interchange of alkyl groups occurs on rapid recrystallisation. 

It follows therefore that ethyl malonate can be used (just as ethyl aceto- acetate) to prepare any mono or di-substituted acetic acid the limitations are identical, namely the substituents must necessarily be alkyl groups (or aryl-alkyl groups such as CjHjCHj), and tri-substituted acetic acids cannot be prepared. Ethyl malonate undergoes no reaction equivalent to the ketonic hydrolysis of ethyl acetoacetate, and the concentration of the alkali used for the hydrolysis is therefore not important. 

An alkyl group activates all nuclear positions, the 0- and p-positions more than the r-position. The activation is not very strong. 

As the alkyl group changes from methyl to [Pg.163]

The influence of alkyl groups has been attributed to the +/ effect operating primarily at the 0- and />-positions (i), and somewhat less strongly at the m-position by relay. Alternatively, the effect is seen as stabilising the transition states for 0- and />-substitution (ii), more than... 

Kinetic data are available for the nitration of a series of p-alkylphenyl trimethylammonium ions over a range of acidities in sulphuric acid. - The following table shows how p-methyl and p-tert-h xty augment the reactivity of the position ortho to them. Comparison with table 9.1 shows how very much more powerfully both the methyl and the tert-butyl group assist substitution into these strongly deactivated cations than they do at the o-positions in toluene and ferf-butylbenzene. Analysis of these results, and comparison with those for chlorination and bromination, shows that even in these highly deactivated cations, as in the nitration of alkylbenzenes ( 9.1.1), the alkyl groups still release electrons in the inductive order. In view of the comparisons just... 

Some observations about the nitration of some polymethylbenzenes have already been made ( 6.3, 6.4). Replacement of an alkyl group has frequently been observed, but quantitative studies are laeking. 

Cumulenic ethers with the 4-positions blocked by alkyl groups can be obtained from bis-ethers, R0-CH2C=C-C(R )(r2)0R, and sodium amide in liquid NHj, applying the... 

A saturated alkyl group does not exhibit functionality. It is not a d -synthon, because the functional groups, e.g. halide or metal ions, are lost in the course of the reaction. It functions as an alkyl synthon. Alkenyl anions (R. West, 1961) on the other hand, constitute d -synthons, because the C = C group remains in the product and may be subject to further synthetic operations. 

Ketones, in which one alkyl group R is sterically demanding, only give the trans-enolate on deprotonation with LDA at —12°C (W.A. Kleschick, 1977, see p. 60f.). Ketones also enolize regioseiectively towards the less substituted carbon, and stereoselectively to the trans-enolate, if the enolates are formed by a bulky base and trapped with dialkyl boron triflates, R2BOSO2CF3, at low temperatures (D A. Evans, 1979). Both types of trans-enolates can be applied in stereoselective aldol reactions (see p. 60f.). 

The introduction of additional alkyl groups mostly involves the formation of a bond between a carbanion and a carbon attached to a suitable leaving group. S,.,2-reactions prevail, although radical mechanisms are also possible, especially if organometallic compounds are involved. Since many carbanions and radicals are easily oxidized by oxygen, working under inert gas is advised, until it has been shown for each specific reaction that air has no harmful effect on yields. 

The simplest case is the substitution of a halogen at a saturated carbon atom by an alkyl group. Organocopper reagents exhibit strong carbanionic capacity, and do attack ester groups only slowly (D.E. Bergbreiter, 1975). Ketones, however, should be protected. The relative re-... 

If alkyl groups are attached to the ylide carbon atom, cis-olefins are formed at low temperatures with stereoselectivity up to 98Vo. Sodium bis(trimethylsilyl)amide is a recommended base for this purpose. Electron withdrawing groups at the ylide carbon atom give rise to trans-stereoselectivity. If the carbon atom is connected with a polyene, mixtures of cis- and rrans-alkenes are formed. The trans-olefin is also stereoseiectively produced when phosphonate diester a-carbanions are used, because the elimination of a phosphate ester anion is slow (W.S. Wadsworth, 1977). 

Cis-olefins or cis./rjns-dienes can be obtained from alkynes in similar reaction sequences. The alkyne is first hydroborated and then treated with alkaline iodine. If the other substituents on boron are alkyl groups, a cis-olefin is formed (G. Zweifel, 1967). If they are cir-alkenyls, a cis, trans-diene results. The reactions are thought to be iodine-assisted migrations of the cis-alkenyl group followed by (rans-deiodoboronation (G. Zweifel, 1968). Trans, trans-dienes are made from haloalkynes and alkynes. These compounds are added one after the other to thexylborane. The alkenyl(l-haloalkenyl)thexylboranes are converted with sodium methoxide into trans, trans-dienes (E. Negishi, 1973). The thexyl group does not migrate. 

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