Primary alkyl structure

Potential energy diagram (Section 4 8) Plot of potential en ergy versus some arbitrary measure of the degree to which a reaction has proceeded (the reaction coordinate) The point of maximum potential energy is the transition state Primary alkyl group (Section 2 13) Structural unit of the type RCH2— in which the point of attachment is to a pnmary carbon... 

Primary alkyl group (Section 2.13) Structural unit of the type RCH2—, in which the point of attachment is to a primary carbon. 

Carboxylic acids can be alkylated in the a position by conversion of their salts to dianions [which actually have the enolate structures RCH=C(0")2 ] by treatment with a strong base such as LDA. The use of Li as the counterion is important, because it increases the solubility of the dianionic salt. The reaction has been applied to primary alkyl, allylic, and benzylic halides, and to carboxylic acids of the form RCH2COOH and RR"CHCOOH. This method, which is an example of the alkylation of a dianion at its more nucleophilic position (see p. 458),... 

The strained hydrocarbon [1,1,1] propellane is of special interest because of the thermodynamic and kinetic ease of addition of free radicals (R ) to it. The resulting R-substituted [ 1.1.1]pent-1-yl radicals (Eq. 3, Scheme 26) have attracted attention because of their highly pyramidal structure and consequent potentially increased reactivity. R-substituted [1.1.1]pent-1-yl radicals have a propensity to bond to three-coordinate phosphorus that is greater than that of a primary alkyl radical and similar to that of phenyl radicals. They can add irreversibly to phosphines or alkylphosphinites to afford new alkylphosphonites or alkylphosphonates via radical chain processes (Scheme 26) [63]. The high propensity of a R-substituted [1.1.1] pent-1-yl radical to react with three-coordinate phosphorus molecules reflects its highly pyramidal structure, which is accompanied by the increased s-character of its SOMO orbital and the strength of the P-C bond in the intermediate phosphoranyl radical. 

C(C=0)C1 group to the precise structure (primary, secondary or tertiary) of the alkyl groups to which it is linked. However, our subsequent work with NO showed that its products are also sensitive to the alkyl structure yet in addition NO reacts with oxidized polymers to give distinctly different products from alcohol and hydroperoxide groups (see below). Consequently the COCl2 products were not explored further. 

Methylation of [Co(tmt)]2+ with Mel leads to the potent methyl carbanion donor trans-[Co(tmt)Me2]+ (186). Reaction of this complex with variety of methyl-lead(IV) compounds in MeCN is rapid, leading to the same monomethylcobalt(III) product, but resulting in different methylated Pb derivatives depending on the reaction stoichiometry and Pb compound.839 The same complex rapidly transfers Me groups to Zn2+ and Cd2+ in MeCN,840 or Pb2+ and Sn2+ in water.302,841 The kinetics of Co—C bond formation in the reactions with primary alkyl and substituted primary alkyl radicals has been found to be influenced more by the structure of the macrocycle than by the nature of the radicals.842... 

The numerous straightforward examples of internal displacement reactions leading to isolable cyclic products will not be discussed here, but only, for the most part, those ionization reactions in which a cyclic intermediate or transition state is deduced from the rearranged structure of the product. A well-known example is mustard gas and other alkyl chlorides with sulfur on the /3-carbon atom. Although mustard gas is a primary and saturated alkyl chloride, its behavior is like that of a typical tertiary alkyl chloride. It reacts so fast by a first order ionization that the rate of the usual second order displacement reaction of primary alkyl halides is not measureable. Only the ultimate product, not the rate, is determined by the added reagent.228 Since the effect of the sulfur is too large to be explicable in terms of a carbon sulfur dipole or similar explanation, a cyclic sulfonium ion has been proposed as an... 

Fig. 2.11.1. General structural formula of (I) primary alkyl sulfonates (PAS) and (II) secondary alkyl sulfonates (SASs).

Structures such as (26) were demonstrated [103] to he fairly easily reduced at a Pt electrode. Thus, when R = Ph, an anion radical (E° = —1.26 V vs Ag/Agl/I 0.1 M) of high stahihty is formed. However, macroelectrolyses of the compounds (26) could not he achieved at all since whatever the amount of electricity passed through the cell, the starting material was totally recovered. The compounds (26) are expected to react slowly with the tetraalky-lammonium salt R4N+ and the reaction would correspond to an indirect reduction of the electrolyte. Compounds (26), with R = primary alkyl groups, led - even in DMF-to strong self-inhibition explained by the adsorption of produced... 

Primary alkyl halide C HgBr (a) reacted with alcoholic KOH to give compound (b). Compound (b) is reacted with HBr to give (c) which is an isomer of (a). When (a) is reacted with sodium metal it gives compound (d), CgH g which is different from the compound formed when n-butyl bromide is reacted with sodium. Give the structural formula of (a) and write the equations for all the reactions. 

The Gabriel synthesis of amines uses potassium phthalimide (prepared from the reaction of phthalimide with potassium hydroxide). The structure and preparation of potassium phthalimide is shown in Figure 13-13. The extensive conjugation (resonance) makes the ion very stable. An example of the Gabriel synthesis is in Figure 13-14. (The N2H4 reactant is hydrazine.) The Gabriel synthesis employs an 8, 2 mechanism, so it works best on primary alkyl halides and less well on secondary alkyl halides. It doesn t work on tertiary alkyl halides or aryl halides. 

When secondary Grignard reagents are used, the coupling product sometimes is derived from the corresponding primary alkyl group.169 This transformation can occur by reversible formation of a nickel-alkene complex from the cr-bonded alkyl group. Reformation of the cr-bonded structure will be preferred at the less hindered primary position. 

Since aprotio sites in the zeolites under study were generated via ion exchange of protons inside crystal volume, the aprotio sites formed are also situated inside crystals. In connection with this, a position selectivity of primary alkylation must be influenced by structural restrictions which are put on the ti nsition state by ZSM-5 type zeolite. Hence, as follows from refs.[6,7], para-isomer must be a primary product of alkylation. Taking into account these ideas,the schemes of the main routes of investigated reactions are accepted (Jigs. 1,2). As seen from the schemes, the pathways of both reactions are practically the same. The only difference is that in the case of ethylbenzene alkylation proceeds... 

The experimental enthalpies of protonation and the formal enthalpies of protonation, RMgBr —RH, are fairly constant for structurally similar species (R = cycloalkyl, primary alkyl) and would be expected to be constant also for the primary cycloalkyhnethyl-magnesium bromides. For the two examples just discussed, the formal enthalpies of protonation that are calculated using the derived enthalpies of formation for the cyclopropyl-and cyclobutylmethyhnagnesium bromides are 262 and 235 kJmoU, respectively. The mean value is thus 248 kJmoU, which is very close to that expected for the formal protonation of other primary R groups. 

This is the case for secondary and tertiary alkyl bromides. If the stability is high, however, as, for example, with primary alkyl bromides, the organo nickel(III) complex is further reduced to an alkyl nickel(II) complex which loses the alkyl group in form of the alkyl anion. An electroinactive Ni(II) species remains. The number of regenerative cycles is consequently low. The structure of the ligand also influences the lifetime of the alkyl nickel(ni) complex thus, a less stable complex is formed in the case of [A,A -ethylene-bis(salicylidene-irainato)]nickel(II) ([Ni(salen)]) as compared with (5,5,7,12,12,14-hexamethyl-l,4,8,ll-tetraazacyclo-tetradecane)nickel(II) ([Ni(teta)] ), and hence the former complex favors the radical pathway even with primary alkyl halides. 

SAMPLE SOLUTION (a) Compare the structures of the two chlorides. 1-Chloro-hexane is a primary alkyl chloride cyclohexyl chloride is secondary. Primary alkyl... 

As revealed by their structural formulas, one isomer is a primary alkyl chloride, the other is secondary. The problem states that the major product (compound A) undergoes SN1 hydrolysis much more slowly than the minor product (compound B). Since secondary halides are much more reactive than primary halides under SN1 conditions, the major (unreactive) product is the primary alkyl halide l-chloro-2,2,4,4-tetramethylpentane (compound A) and the minor (reactive) product is the secondary alkyl halide 3-chloro-2,2,4,4-tetramethylpentane (compound B). 

They assumed that the primary cation radical of PMMA spontaneously and quickly dissociated to form carbocation, which then recombined with the liberated electron to form an excited radical with a ferr-alkyl structure. This excited radical was thought to be the precursor of the scission of the main chain. This reaction model interpreted well their observation that the G value for the scission of the side chain was close to that of the main chain and that the mercaptan added to scavenge electrons suppressed the main-chain scission efficiently without affecting the formation of volatile products from the ester side chain. The above reaction model motivated us to apply the ESE method to the study of radicals in irradiated PMMA. The model now seems inadequate, because it cannot accommodate some recent ESE results as mentioned later. 

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