Structural Effects on the Properties of Nonionic Surfactants. I. The Synthesis and Some Surface Activities of Acetal Type Homogeneous Nonionics

Higher aliphatic aldehydes (C8–C16) were treated in the presence of mineral acid with several pure polyoxyethylene glycols (m : 2–6), to give the corresponding acetals (AG types) with a general formula RCH[O(C2H4-O)mH]2. These AG types are soluble in water, fairly stable in neutral and weakly basic aqueous solutions, and they exhibited the characteristic properties of nonionics. The hydration of the geminal polyoxyethylene (POE) chains are discussed on the basis of the data of unexpectedly low cloud points. Surface tension measurements on the aqueous solutions of AG types indicated that the critical micelle concentration (CMC) value decreases with an increment of oxyethylene units (m), and that the molecular area does not depend so greatly on m and is significantly smaller than that predicted from the data of conventional nonionics (S types) having one hydrophobic and hydro-philic chain each. For the gross effects of AG types, it has been found that the foam stability is considerably low and the dependence of the wetting power for canvas discs on m is larger than that of S types. The results are discussed on the basis of structural characteristics related to the unfavorable hydration and restricted configuration of the geminal POE chains. The acid-catalyzed hydrolysis of AG types in the micellar solution was significantly slower than that of acetaldehyde diethylacetal in water.