Dodecanethiol Research Articles

S-methyl derivatives from thiol compounds by the pyrolytic reaction with trimethylsulfonium hydroxide.

Base-catalyzed transesterification of acyl lipids with methanol in the presence of trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters for gas chromatography (GC) analyses. Free fatty acids are converted to fatty acid methyl esters by the pyrolytic reaction with TMSH as well. We have found that lipids and other compounds containing thiol groups are also converted easily to the corresponding methyl sulfides (methyl thioethers) by the pyrolytic reaction with TMSH occurring in the injector of the gas chromatograph. For example, alkane thiols such as dodecane thiol and octadecane thiol are converted to the corresponding alkyl methyl sulfides, whereas bis(methylthio) derivatives are formed from alpha,omega-alkane dithiols, e.g., 1,8-octanedithiol, and from 2,3-dimercaptopropan-1-ol (dimercaprol). Furthermore, 3beta-mercaptocholest-5-ene (thiocholesterol) is converted to 3-methylthiocholest-5-ene by the same reaction. The S-methylation reactions which finally lead to the corresponding methylthio derivatives of lipids and other compounds with thiol groups may be of diagnostic value for the structural analysis of such compounds by GC and GC/mass spectrometry.

Formation of organic thin films at the liquid-solid interface studied by second harmonic spectroscopy

Self-assembly of ω-(p-nitroanilino) dodecane thiol (p-O 2N-C 6H 4-NH-(CH 2) 12SH) (NAT) on polycrystalline gold films by adsorption from solution was studied in situ with second harmonic generation (SHG). Depending on the wavelength different parts of the system are probed. At a fundamental wavelength of 1 064 nm thiol adsorption is monitored in real time by the formation of the sulfur-substrate bond. A linear dependence of the non-linear susceptibility from the thiol coverage describes the time-dependent SH signal quantitatively. In contrast, the nitroaniline (NA) end group measured at a SH wavelength of 350 nm exhibits a very different behavior. Phase-sensitive measurements carried out in situ reveal that an increase of the density of the film causes the phase of the SH signal from the NA moiety to advance. This phase shift which corresponds to a blue-shift of the resonance becomes effective for coverages higher than 0.4 and is explained by the repulsive interaction of the NAT molecules.

Self-assembly of short and long-chain n-alkyl thiols onto gold surfaces: A real-time study using surface plasmon resonance techniques

Gold surfaces coated with monolayers of alkyl thiols are significant in the field of biosensors and chromatography. There is a general concern about the quality of coatings in terms of surface density and voids. The self-assembly of the short-chain hexane (C6) thiol and long-chain dodecane (C12) and hexadecane (C16) thiols to polycrystalline gold surfaces has been investigated in situ and in real time using surface plasmon resonance (SPR) spectroscopy and surface plasmon microscopy (SPM). The self-assembly was followed based on observed changes in reflectivity at a fixed angle of incidence as a function of time. Our results indicate that the data for hexane, dodecane, and hexadecane thiol adsorption to gold surfaces were best fit by a two-step process rather than a one-step process. The mechanism may involve fast adsorption to the surface to give 80% (C12, C16) or 50% (C6) coverage followed by a slow (100-fold slower) "rearrangement" of the adsorbed thiol. SPM shows these surfaces to be smooth and homogenous at a 4 μm scale. An understanding of the process of rearrangement could lead to control of the quality of coatings for analytical applications. Key words: surface plasmon, alkyl thiols, gold, monolayer, kinetics, ellipsometry, microscopy.

Télomérisation radicalaire du méthacrylate de glycidyle avec le benzène thiol et le dodécane thiol

The radical telomerization of glycidyl methacrylate (MAG) with benzene thiol and dodecane thiol and initiated by u.v. radiation has been studied. The transfer constant to these telogens at 38° (1.76 for benzene thiol and 0.31 for dodecane thiol) are calculated using cumulated DP n [( DP n ) cum ] and monomer conversion factor α of the reactions. It is verified that, when C T is > 1, ( DP n ) cum increases with increasing α. On the other hand, if C T is lower than < 1 ( DP n) cum decreases with increasing α. The experimental results also confirm that R 0 is the limit of 1 (DP n ) cum at complete conversion.

Stndies on the Special Type Surfactants. IV.

Solution polymerization of methyl acrylate was carried out using 1-dodecanol (ROH), 1-chloro dodecane (RCl), 1-dodecanoic acid (RCOOH), 1-dodecyl amine (RNH2), or 1-dodecane thiol (RSH) as solvent and benzoyl peroxid (BPO) as an initiator.When ROH, RCl or RCOOH was used as solvent the degree of polymerization of telomers (LO, LC and LA series) obtained were 1022 and ROH was the most excellent solvent in point of yield and low degree of polymerization. On the other hand, use of RNH2 as solvent gave N, N'-didodecyl-β-amino propionamide (LN-A) and its polymer (LN-AA), while use of RSH as solvent yielded 1 : 1-addition product, disulfide and telomer (Pn=2.4).The chemical structures of these products were determined by their molecular weight, elementary analyses and IR spectra. These telomers were treated with water-acetone alkaline solution to obtain the corresponding polyacrylic acid.The surface active properties of these saponified telomers are as follows : Their surface tension generally showed a high value, but high saponified LO series had a low value (<30 dyne/cm). Relation between cmc and Pn of LO series was log cmc=0.0549PPn-1.80.Low saponified telomers showed good value on emulsifying, but bad on dispersing power.