3-ethyl-3-pentyl radical

Flowers M C and Rabinovitch B S 1985 Localization of excitation energy in chemically activated systems. 3-ethyl-2-methyl-2-pentyl radicals J. Rhys. Chem. 89 563-5... 

Rrst of all, carbon-carbon bond breakings give the methyl, ethyl, propyl, butyl, and pentyl radicals, which can abstract hydrogen to give methane, ethane, propane, butane, and pentane ... 

It is interesting to note that lactones 42-46, 51 corresponding to the above tetrahydropyrans 109-114 (with the exception of 125, the precursor to 115) showed a similar but attenuated trend in activities. For example, lactones 43 and 44 were most potent in this series (ethyl and propyl) at about 12 times the activity of artemisinin, and had dropped significantly in potency by butyl (45) and pentyl (46). Similarly, 3-phenylpropyl lactone 51 was reasonably potent at 4-6 times control. It is clear that removal of the lactone carbonyl in the series 108-115 provides excellent potency enhancement and that overall trends relative to lactones 42-46, 51,125 are not radically altered, but do seem to be offset somewhat (e.g. ethyl most potent in lactone series butyl most potent in tetrahydropyran series). 

Tertiary alcohols are oxidized in water-dioxane-NaOH to alkoxy radicals, wliich fragmentate to ketone and alkyl radicals R- (Eq. (216) ). The relative rate of cleavage decreases with R in the order sec -butyl > isopropyl > ethyl > propyl > pentyl > isobutyl > methyl 46 8). Likewise, the bisulfite adduct of cyclohexanone is converted in 20% yield to 4-hydroxyhexanoic acid lactone (160) and 3-hydroxycyclohexanoic acid lactone (161) by anodic fragmentation (Eq. (222) ) 469 ... 

As O Neal and Benson have pointed out, only six of the group values are linearly independent one can be assigned arbitrarily. As they did, we choose to set / = P. The other six terms can be calculated from experimentally determined enthalpies of formation of the radicals ethyl, n-propyl, i-propyl, t-butyl, i-butyl and neo-pentyl. The enthalpy of 5-butyl can be substituted for that of either n-propyl or i-propyl. The relationships are as follows ... 

To investigate the detailed structures and energetics of the initiation reaction for a larger system, the four possible reaction pathways to break the C-C bonds in an octane molecule have been studied (Goldstein et al. 1996 Xiao et. al. 1997). Table 3 shows the reaction scheme for octane cracking with four pairs of products—methyl and heptyl, ethyl and hexyl, propyl and pentyl, and butyl and butyl radicals. The calculated BDEs of these homolytic C-C scission at the MP2/6-31G, PMP2/6-31G, B3LYP/6-31G, and CBS-4 levels, are also listed in Table 3. 

To investigate the possible molecular size effect on the calculated energetics, the P scission reactions of a primary pentyl, hexyl, and heptyl radical have also been studied (Xiao et al. 1997). The calculated activation energy Ea and heat of reaction AH at the B3LYP/6-31G level are 30.43 and 23.41 kcal/mol for butyl O ethylene + ethyl 30.52 and 23.58 kcal/mol for pentyl o ethylene + propyl 30.38 and 23.35 kcal/mol for hexyl ethylene + butyl and 30.39 and 23.37 kcd/mol for heptyl O ethylene + pentyl. The results again suggest that the kinetics is largely controlled by the type of reaction, rather than the size of the system. 

The pentyl and ethyl radicals can be formed by peroxidation of linoleic acid at C-13, of linolenic acid at C-16, and of arachidonic add at C-15 when rat liver microsomes were incubated with ADP, NADPH and ferric chloride (Iwahashi et al. 1992). 

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