TY - JOUR
T1 - Trialkylammonium mixed salts in amine extraction systems. infrared study of the salts (R3NH3CPMo12O40] AND (R3NH)C1 AND MIXED SALT (R3NH3LPMo12O40J].3(R3NH)Cl
AU - Moyer, Bruce A.
PY - 1988/1/1
Y1 - 1988/1/1
N2 - Infrared spectrophotometry has been used to compare the hydrogen-bonding (H-bonding) interactions in the set of solid trialkylammonium salts and double salts (R3NH)3[DMP], (R3NH)C1, and (R3NH)3[DMP]•3(R3NH)Cl (A), where R represents a straight or methyl-branched alkyl group containing 8 to 13 carbons and DMP is the large dodecamolybdophosphate anion PMo12O403-. Through an examination of the characteristic heteropolymolybdophosphate vibrational bands of A and (R3NH)3[DMP], the complex anion is identified as α-DMP ad shown to be in an environment chemically similar to its tetrabutylammonium salt. A relatively weak H-bond in (R3NH)3[DMP] is indicated by small downward shifts in the N-H stretching frequencies vnh of the trialkylammonium cations from the hypothetical free-ion value. By contrast, large shifts in vnh induced by strong H-bonding occur in the salts (R3NH)C1. In the double salts A, the intermediate value of vnh suggests the existence of complex cations like [R3NH•• •C1 ••• HNR3]. The effect of amine structure on the infrared spectra is minor in all of the compounds studied except that methyl-branching increases the downward shift of the N-H stretching frequency of the salts (R3NH)Cl; this is Interpreted as evidence that methyl branching strengthens the H-bond by decreasing the basicity of the parent amine. Density and unit-cell data are also reported for some of the DMP-containing compounds. Possible relationships between the present results and previously observed solubility patterns are discussed.
AB - Infrared spectrophotometry has been used to compare the hydrogen-bonding (H-bonding) interactions in the set of solid trialkylammonium salts and double salts (R3NH)3[DMP], (R3NH)C1, and (R3NH)3[DMP]•3(R3NH)Cl (A), where R represents a straight or methyl-branched alkyl group containing 8 to 13 carbons and DMP is the large dodecamolybdophosphate anion PMo12O403-. Through an examination of the characteristic heteropolymolybdophosphate vibrational bands of A and (R3NH)3[DMP], the complex anion is identified as α-DMP ad shown to be in an environment chemically similar to its tetrabutylammonium salt. A relatively weak H-bond in (R3NH)3[DMP] is indicated by small downward shifts in the N-H stretching frequencies vnh of the trialkylammonium cations from the hypothetical free-ion value. By contrast, large shifts in vnh induced by strong H-bonding occur in the salts (R3NH)C1. In the double salts A, the intermediate value of vnh suggests the existence of complex cations like [R3NH•• •C1 ••• HNR3]. The effect of amine structure on the infrared spectra is minor in all of the compounds studied except that methyl-branching increases the downward shift of the N-H stretching frequency of the salts (R3NH)Cl; this is Interpreted as evidence that methyl branching strengthens the H-bond by decreasing the basicity of the parent amine. Density and unit-cell data are also reported for some of the DMP-containing compounds. Possible relationships between the present results and previously observed solubility patterns are discussed.
UR - http://www.scopus.com/inward/record.url?scp=84915931746&partnerID=8YFLogxK
U2 - 10.1080/07366298808917922
DO - 10.1080/07366298808917922
M3 - Article
AN - SCOPUS:84915931746
SN - 0736-6299
VL - 6
SP - 1
EP - 37
JO - Solvent Extraction and Ion Exchange
JF - Solvent Extraction and Ion Exchange
IS - 1
ER -