Primary carbon atoms

These reactions indicate that the residue three primary carbon atoms ending in a group... 

The one general exception to the rule that ethers don t typically undergo Sn2 reactions occurs with epoxides, the three-membered cyclic ethers that we saw in Section 7.8. Epoxides, because of the angle strain in the three-membered ring, are much more reactive than other ethers. They react with aqueous acid to give 1,2-diols, as we saw in Section 7.8, and they react readily with many other nucleophiles as well. Propene oxide, for instance, reacts with HC1 to give l-chloro-2-propanol by Snj2 backside attack on the less hindered primary carbon atom. We ll look at the process in more detail in Section 18.6. 

In most paraffins there will be different numbers of hydrogens attached to the carbon atoms. There are four types of carbon atoms with names corresponding to the number of bonds made with other carbon atoms or functional groups. These names are primary, secondary, tertiary, and quaternary, as shown above. In a compound such as isopentane, there are three primary carbon atoms, one secondary, and one tertiary. 

In Table 4,3°, 2°, and 10 represent tertiary, secondary, and primary carbon atom, respectively (Figure 10), and 3°(2°) represents correction for a tertiary carbon bonded to a secondary, as in a methine group to a methylene. In a study conducted... 

Thus, the rule of Keulemans (49), that a-quaternary carbon formyl compounds are not formed, was followed. The olefin isomerized to allow formyl attachment to a primary carbon atom. Addition of phosphine, which decreases isomerization, resulted in no reaction. 

Ethylene oxide rings have as yet been introduced only at the ends of hexitol molecules by hydrolysis of suitable substituents attached to primary carbon atoms, so no question of Walden inversion has arisen. 

The carbanion derived from dimethyl malonate reacts with the cyclic nitro compounds 422 of ring size 5, 6, 7, 8 and 12 to afford the corresponding esters 423. Acyclic allylic nitro compounds 424 (R = Me, CH2OAC or CC Et) are attacked by bulky nucleophiles, such as dimethyl malonate anion, mainly at the terminal primary carbon atom to give rearranged products 425, whereas smaller nucleophiles, e.g. the anion derived from methyl cyanoacetate, react at the tertiary carbon atom to yield 426409a 453 455. 

Figure 4 in Scheme 2.3-2 reveals that with comparable and Pt-intermediary complexes, differences in local symmetries may result. In addition, Ni promotes interactions with a primary carbon atom of the a-allyl group whereas Pt interacts with the substituted carbon atom of this group. 

Only the third supposition is critical. Let us therefore look closer at the exchange of elementorganic groups for halogen. The most important case is the exchange of a group attached to a primary carbon atom (Scheme 12). The exchange is less prob-... 

In comparable reaction conditions as Pd +Cu +Y, Pd + and Cu2+ exchanged pentasil and ferrierite zeolites show a different type of activity [31]. The main products formed by propylene oxidation on these catalysts are acrolein and propionaldehyde below 120°C and 2-propanol above 120 C. Above 150°C consecutive oxidation of 2-propano1 to acetone is observed. The catalytic role of Pd and Cu in the 2-propanol synthesis is proposed to follow the Wacker concept. It is striking that when Pd + and Cu2+ are exchanged in 10-membered ring zeolites, oxidation of a primary carbon atoms seems possible, as acrolein and propionaldehyde are obtained from propylene. 

These enzymes are systematically named nucleoside 5 -(o -D-glycopyranosyl pyrophosphate) NAD oxidoreductases (E.C. 1.1.1 group). It should be noted that only a few enzymes are known, except for the ones just mentioned, that catalyze oxidation of a primary carbon atom to a carboxylic acid group. 

Selective denitration of methyl 4,6-O-benzylidene- and 4,6-O-alkyl-idene-D-hexopyranoside 2,3-dinitrates to yield 3-nitrates has also been achieved by using sodium nitrite in ethanol as the reagent.233,238, 241.242 interestingly, when the nitrate group is on a primary carbon atom, reaction with this reagent takes place to give the primary alcohol,232,241,243 but the conversion may, on occasion, proceed only with... 

Walden inversion has been found at a primary carbon atom by the use of a chiral substrate containing a deuterium and a hydrogen atom at the carbon bearing the leaving group.8 Inversion of configuration has also been found for Sn2 reactions proceeding in the gas phase.9... 

Chlorine monofluoride in nonpolar solvents is a more powerful electrophilic agent than hexa-chloromelamine in hydrogen fluoride. The latter is unable to substitute bromine at primary carbon atoms reacting only with tertiary and secondary bromides.106... 

Since carbocations do not readily abstract hydride ion from secondary (or primary) carbon atoms, n-alkanes seldom enter the alkylation reaction unless they first isomerize to isoalkanes containing tertiary carbon atoms. 

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