Nature of the Alternate CF₂CH₂ Chain:  Study Based on the Measurement and Comparison of the CAgC's of Aggregators with Alternate Chains and with Hydrocarbon Chains

Abstract

The saponification rate constants of p-nitrophenyl esters of carboxylic acids with the hydrocarbon chain and the alternate CF2CH2 chain, i.e., H(CH2CH2)(m-1)/2COOC6H4NO2 (C-m) and Cl(CF2CH2)(m-1)/2-COOC6H4NO2 (AL-m), in which m stands for the number of chain-carbon atoms and is equal to 3, 5, 7, 9, 11, and 13, have been measured in the 20:80 (v/v) (Φ ) 0.20) buffered dioxane-H2O binary solvent. Meanwhile, the fluorescence spectra of 2-(R-naphthyl)ethyl esters of carboxylic acids with the hydrocarbon chain and the alternate CF 2CH2 chain, i.e., H(CH2CH2)(m-1)/2COOCH2CH2C10H7 (Fl-C-m) and Cl(CF2CH2)(m-1)/2COOCH2CH2 C10H7 (Fl-AL-m) (m ) 3, 5, 7, 9, 11, and 13) have been measured in the Φ ) 0.20 dioxane-H2O solvent system. Critical aggregate concentration (CAgC) values derived from the aforesaid kinetic and spectral measurements revealed that the alternate chain possesses a smaller tendency toward aggregation than the hydrocarbon chain does. Therefore, the alternate CF2CH2 chain seems to possess a minute degree of polarity. It has been shown that even neutral organic molecules with a threecarbon chain could show some aggregating tendencies, and our results imply that simple aggregates are formed by a stepwise process.

Effect of coaggregate formation on the fluorescence quenching of anthracene derivatives bym-N,N-diethyl-­aminophenyl carboxylates with different chain lengths as quenchers

“…Finally, aggregation and coaggregation are consequences of stepwise processes. 19 For the measurement of CAgC or CoCAgC values based on propertyconcentration plots there is usually a transition region. Since measurements at these extremely low concentrations are not very precise, the intercept value at zero concentration may not be unity.…”