No abstract

Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification “DE” and on molecular weight “Mw”. Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x1005 to 2.47x1005 g/mol for grapefruit pectin and from 1.639 x1005 to 2.471 x1005 g/mol for orange pectin.

For PPh 3 , mixtures of Pd(dba) 2 and nTFP (TFP ) tri-2-furylphosphine, n g 2) in DMF and THF (S) lead to the formation of Pd(dba)(TFP) 2 , SPd(TFP) 3 in equilibrium with SPd-(TFP) 2 . The substitution of dba by the phosphine in Pd(dba)L 2 to form SPdL 3 is easier for L ) TPF than for L ) PPh 3 . The less ligated complex SPd(TFP) 2 is the reactive species in the oxidative addition with phenyl iodide. In THF, {Pd(dba) 2 + nTFP}, a mixture often used as a catalyst promoter in several synthetic organic reactions, is found to be less reactive than {Pd(dba) 2 + nPPh 3 } for small values of n (n ) 2 or 4) whereas it is more reactive for higher values of n (n > 6). Conversely, in DMF, {Pd(dba) 2 + nTFP} is always found to be more reactive than {Pd(dba) 2 + nPPh 3 } whatever n (n g 2).