Other Substituted Alkyl Groups

Reductive conversion of hydroxymethyl to methyl during the catalytic hydrogenation of 6- and 7-hydroxymethylpterins (e.g. 703 — 706) probably involves H20 elimination from the intermediate 5,8-dihydro species (704) and subsequent reduction of the C = C and C = N bonds in (705) (B-89MI 718-02). 

Compounds of type Het-CH2CH2X where X is a leaving group (e.g. halogen, OR, NR2, SR, etc.) undergo reverse Michael reaction via 

2-(Diazomethyl)pyridine (708) which normally exists in the ring-closed form (707) thermolyzes to 2-pyridylcarbene (709) which interconverts in the gas phase with phenylnitrene (711). Photolysis of 2-(diazomethyl)pyridine in an argon matrix allows identification of l-aza-l,2,4,6-cycloheptatetraene (710). 3- and 4-Pyridylcarbenes also interconvert with phenylnitrene (81AHC(28)279). 

Trihalomethyl groups can be replaced in nucleophilic substitution reactions in sufficiently activated systems, as for example in. v-triazines. 2,4,6-Tris(trichloromethyl)-.v-triazine is converted into 2,4,6-triamino-.v-triazine by ammonia. 

2-(a-Hydroxyalkyl) groups are removed by nucleophiles in retro-aldoF type reactions. The heterocycle is eliminated as the zwitterion species, or nucleophilic carbene (712). 

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Other substituted alkyl groups. N-Allyl compounds can be rearranged to N-propenyl derivatives. Similarly, N-propargyl salts 1011 give N-allenyl derivatives 1012. 

Usually, the reactions are complete within hours and give good conversions (40% -90+%). In general, the larger the alkyl or other substituted alkyl group on the ester, the slower the reaction rate. Heteroatom containing substituents do not have a... 

Polythiophenes with substituents other than alkyl groups at the 3 position have been prepared by the polymerization of substituted monomers. Many of these polymers have been substituted alkylthiophenes (8) where example side chains are (R =) —(86—89), —OCH (68), —NHC(0) (CH2) qCH (6 )) —0502(0112)30112 (90). Ohiral side chains have also been employed (91,92). Poly(3-alkoxythiophenes) (9) (93—95) and... 

The latter reagent also methylates certain heterocyclic compounds (e.g., quinoline) and certain fused aromatic compounds (e.g., anthracene, phenanthrene). The reactions with the sulfur carbanions are especially useful, since none of these substrates can be methylated by the Friedel-Crafts procedure (11-12). It has been reported that aromatic nitro compounds can also be alkylated, not only with methyl but with other alkyl and substituted alkyl groups as well, in ortho and para positions, by treatment with an alkyllithium compound (or, with lower yields, a Grignard reagent), followed by an oxidizing agent such as Bra or DDQ (P- 1511). 

When a hydrocarbon is substituted with other than alkyl groups a new problem arises, which can be illustrated by CH3CH2C1. This substance can be called either chloroethane or ethyl chloride, and both names are used in conversation and in print almost interchangeably. In the IUPAC system, halogens, nitro groups, and a few other monovalent groups are considered to be substituent groups on hydrocarbons and are named as haloalkanes, nitro-alkanes, and so on. 

Charton80 tabulates 07 values for several of the alkyl-substituted vinyl groups which are components of the acids discussed in the present section, as well as values for other substituted vinyl groups, such as chloro-substituted groups. A selection is shown in Table 4. 

Nucleophilic aliphatic substitution was believed some years ago to take place by two distant paths, one involving a one-step displacement, the other an intermediate carbonium ion. These two routes can be represented as follows, for the reaction between RX (R being an alkyl or substituted alkyl group) and a nucleophile Y-... 

Ethers are quite unreactive, relative to many other functional groups we study, and are often used as solvents for that reason. Concentrated halogen acids can cleave ethers to alcohols and halides. Remember that the halide is bonded to the less substituted alkyl group when the ethers are primary or secondary alkyl ethers. 

In the 1950s, a new class of musks was discovered, the polycyclic musks. These materials mostly have indane, tetralin or isochroman structures, heavily substituted by methyl or other small alkyl groups. Typical members of this family are Traseolide (42), Phantolide (43) and Celestolide /Crysolide (44). 

Substituting the methyl groups with other higher alkyl groups increases the surface tension of the polymer246. 

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