Kinetics of Hydroformylation of 1-Dodecene in Microemulsion Systems Using a Rhodium Sulfoxantphos Catalyst

Solubilization of Aldehydes and Amines in Aqueous CiEj Surfactant Aggregates: Solubilization Capacity and Aggregate Properties

Hydroformylation of olefins to aldehydes and subsequent reductive amination of aldehydes to amines takes place in an aqueous system using a water-soluble catalyst. It is limited to short-chain molecules due to an insufficient solubility of long-chain molecules in water. A promising approach to increase the solubility of long-chain aldehydes and amines is the addition of surfactants to the aqueous phase. In this work, we thus determined the solubilization capacity (SC) of different nonionic C_iE_j surfactants (C₈E₆, C₁₀E₆, and C₁₀E₈) toward long-chain aldehydes and amines. We used static and dynamic light scattering techniques to investigate the influence of both the surfactant and solute molecular structures on the SC as well as on the aggregation number (N_agg) and hydrodynamic radius (R_h) of mixed aggregates. Our data reveals that an optimum ratio of hydrophobic to hydrophilic chain length of C_iE_j surfactants exists where the SC toward long-chain aldehydes and amines possesses a maximum. Further, the size of the aggregates (N_agg, R_h) passes through a minimum upon amine solubilization, while upon aldehyde solubilization, the aggregate size increases gradually. The results shown in this work give valuable insights to the solubilization of aldehydes and n-amines into nonionic C_iE_j surfactants and facilitate the search of suitable surfactants for hydroformylation and reductive amination as "green" solvents based on the detailed knowledge about the aggregate structure.

One-Pot Synthesis of Fatty Amines: Rh-Catalyzed Hydroaminomethylation of 1-Decene in an Aqueous Microemulsion System—Influence of Reaction Conditions on the Reaction Performance

The hydroaminomethylation of the long-chain olefin 1-decene and diethylamine with a homogeneous Rh(acac)(cod)/SulfoXantphos catalyst complex as a one-pot synthesis was investigated. The influence of reaction conditions such as temperature and synthesis gas pressure was determined, as well as the effects of the initial concentrations of catalyst precursor, ligand, and reactants on the yield of fatty amine. Hydroaminomethylation was successfully carried out in an aqueous microemulsion system using a non-ionic surfactant with a reaction time of 2 h. A maximum yield of 34%, high regioselectivities >97%, and chemoselectivities >85% were achieved.

Influence of Temperature and Concentration on the Self-Assembly of Nonionic CiEj Surfactants: A Light Scattering Study

Nonionic poly(ethylene oxide) alkyl ether (C_iE_j) surfactants self-assemble into aggregates of various sizes and shapes above their critical micelle concentration (CMC). Knowledge on solution attributes such as CMC as well as aggregate characteristics is crucial to choose the appropriate surfactant for a given application, e.g., as a micellar solvent system. In this work, we used static and dynamic light scattering to measure the CMC, aggregation number (N _agg), and hydrodynamic radius (R _h) of four different C_iE_j surfactants (C₈E₅, C₈E₆, C₁₀E₆, and C₁₀E₈). We examined the influence of temperature, concentration, and molecular structure on the self-assembly in the vicinity of the CMC. A minimum in the CMC vs temperature curve was identified for all surfactants investigated. Further, extending the hydrophilic and hydrophobic chain lengths leads to an increase and decrease of the CMC, respectively. The size of the aggregates strongly depends on temperature. N _agg and R _h increase with increasing temperature for all surfactants investigated. Additionally, N _agg and R _h both increase with increasing surfactant concentration. The data obtained in this work further improve the understanding of the influence of temperature and molecular structure on the self-assembly of C_iE_j surfactants and will further foster their use in micellar solvent systems.

Rh-Catalyzed Reductive Amination of Undecanal in an Aqueous Microemulsion System Using a Non-Ionic Surfactant

The homogeneously catalyzed reductive amination of the long-chain aldehyde undecanal with diethylamine was performed in an aqueous microemulsion system using the non-ionic surfactant Marlophen NP8. The experiments showed that the used water-soluble rhodium/SulfoXantphos catalyst system is suitable for this reaction. The Rh-catalyzed formation of the alcohol by-product can be completely suppressed by the use of carbon monoxide with its stabilizing effect of the catalyst system. In addition to pressure and temperature, the most important parameters for the reaction performance of the reductive amination are the concentrations of reactants. Especially, the initial concentration of the aldehyde has a strong impact on the chemoselectivity, and the formation of aldol by-product due to the fact that both, the enamine condensation and the aldol condensation are equilibrium reactions.