Kinetics of base-catalyzed degradation of phenyl d-gluco-pyranosides

doi:10.1016/S0008-6215(00)84626-1

Carbohydrate Research

Volume 75, October 1979, Pages 51-59

https://doi.org/10.1016/S0008-6215(00)84626-1 Get rights and content

Abstract

The kinetics of base-catalyzed cleavage of the glycosidic linkage in phenyl α- and β-d-glucopyranoside have been studied at various concentrations of base, and are interpreted in terms of formation of anionic species as reactive intermediates, accompanied by a minor mechanism of bimolecular, nucleophilic substitution.

The data indicate that, in <M sodium hydroxide solution, more than 80% of the cleavage reaction proceeds through an intramolecular-displacement process facilitated by the anchimeric assistance of the hydroxyl group at C-6, and C-2, for the α- and β-d-glycoside, respectively. However, the bimolecular substitution reaction becomes increasingly apparent as the alkalinity is raised above 1.5M concentration of base.

References (16)

Y.-Z. Lai
Carbohydr. Res.
(1972)
C.K. DeBruyne et al.
Carbohydr. Res.
(1974)
C.E. Ballou
Adv. Carbohydr. Chem.
(1954)
F. Shafizadeh et al.
Carbohydr. Res.
(1972)
R.C. Gasman et al.
J. Org. Chem.
(1966)
E.V. Best et al.
Tappi
(1969)
J.H. Robbins et al.
Tappi
(1969)
C.S. Tsai et al.
J. Org. Chem.
(1972)

There are more references available in the full text version of this article.

Cited by (17)

Nano-cellulose reinforced starch bio composite films- A review on green composites
2021, International Journal of Biological Macromolecules
Citation Excerpt :
Additionally, cellulose fibers/starch degraded in 40 days, whereas acetylated cellulose fibers/starch films degraded in 60 days. Cellulose fibers/starch and acetylated cellulose fibers/starch films were reported to have greater resistance due to the higher crystalline and denser structure of cellulose nanofibers which restricted the enzymatic degradation and cellulose hydrolysis [104]. The thick layer of water due to the cellulose crystallinity is responsible for preventing spreading cellulose-degrading enzymes and other substances around the cellulose [105].
Plastic-based food packaging is generating a serious environmental problem by accumulating large amounts of plastic in the surroundings. Ecological and health concerns are driving research efforts for developing biodegradable films. There are few alternatives that could reduce the environmental impact; one of them is to substitute petroleum-based plastic with starch-based film. Starch has remarkable properties, including biodegradability, sustainability, abundancy, and capable of being modified or blended with other polymers. However, low mechanical strength and low water resistance restrict its application in food packaging. Nanocellulose isolated from lignocellulosic fibers has attracted tremendous interest in the field of science due to high crystallinity and mechanical strength, unique morphology along with abundancy, renewability, and biodegradability. Therefore, nano cellulose as a reinforcer proved to be a good option for fabricating biocomposites for food packaging. The current review will give a critical snapshot of the potential application of nanocellulose in food packaging and discuss new challenges and opportunities for starch biocomposites enriched with nano cellulose.
Biodegradability and mechanical properties of reinforced starch nanocomposites using cellulose nanofibers
2015, Carbohydrate Polymers
Citation Excerpt :
It could be observed that the CNFs/TPS and the ACNFs/TPS nanocomposites had a higher degradation resistance compared to the neat TPS. This might be due to the higher crystallinity and the denser structure of the CNFs, which was added to the starch matrix and restricted the destructive enzymatic activities as well as the enzymatic hydrolysis of the cellulose (Lai & Ontto, 1979). The crystalline structure of the cellulose causes the formation of a dense layer of water, which consequently prevents the spread of cellulose-degrading enzymes and other substances around the cellulose (Matthews et al., 2006).
In this study the effects of chemical modification of cellulose nanofibers (CNFs) on the biodegradability and mechanical properties of reinforced thermoplastic starch (TPS) nanocomposites was evaluated. The CNFs were modified using acetic anhydride and the nanocomposites were fabricated by solution casting from corn starch with glycerol/water as the plasticizer and 10 wt% of either CNFs or acetylated CNFs (ACNFs). The morphology, water absorption (WA), water vapor permeability rate (WVP), tensile, dynamic mechanical analysis (DMA), and fungal degradation properties of the obtained nanocomposites were investigated. The results demonstrated that the addition of CNFs and ACNFs significantly enhanced the mechanical properties of the nanocomposites and reduced the WVP and WA of the TPS. The effects were more pronounced for the CNFs than the ACNFs. The DMA showed that the storage modulus was improved, especially for the CNFs/TPS nanocomposite. Compared with the neat TPS, the addition of nanofibers improved the degradation rate of the nanocomposite and particularly ACNFs reduced degradation rate of the nanocomposite toward fungal degradation.
Sucrose decomposition in aqueous solution, and losses in sugar manufacture and refining
1997, Advances in Carbohydrate Chemistry and Biochemistry
This chapter elaborates sucrose decomposition in aqueous solution and losses in sugar manufacture and refining. D-Glucose and D-fructose are present in both cane and beet juice and decompose on the addition of lime at high temperatures during purification of the juice. In addition to direct sucrose loss to invert sugar, undesirable dark-colored products can form in the juice through the Maillard reaction of amino acids and reducing sugars. The reversible reactions are initiated by the equilibrium between neutral and ionized forms of the monosaccharides. The oxyanion at the anomeric carbon weakens the ring C-O bond and allows mutarotation and isomerization through an acyclic enediol intermediate. This reaction is responsible for the sometimes reported occurrence of D-mannose in alkaline mixtures of sucrose and invert sugar. An important consequence of sucrose degradation is the development of color from degradation products. An equation for the prediction of color development in model sucrose solutions is developed in the chapter. It is found that the number of water molecules in the sucrose solvation shell depends on the extent of intramolecular hydrogen-bonding in the sucrose molecule.
Chapter 11 Glycosyl transfer
1984, New Comprehensive Biochemistry
Many glycosyl-transfer reactions and similar reactions involving acetals and ketals are written as involving a discrete oxocarbonium ion. Proof of the reality of such an intermediate is its direct observation and the demonstration that it has a sensible lifetime under the conditions of the reaction. Two criteria can be applied for the sensibleness of the lifetime of reactive intermediate. An absolute, conceptual one is that the lifetime must be longer than the period of a bond vibration, ∼10^-13 sec. A less exacting one is that the intermediate lives long enough for any other part of the precursor molecule to diffuse away: in water at 25^°C, this gives a lower limit of ∼10^-10 sec. Some exceptionally stable oxocarbonium ions can be observed in neutral aqueous solutions: others can be observed in aqueous sulphuric acid and their lifetimes extrapolated to pure water. O-methylated acetophenone is a fairly stable oxocarbonium ion, yet its lifetime is approaching the region in which its existence could be called into question.
A re-investigation of the kinetics of alkaline degradation of phenyl β-d-glucopyranoside and some other glycosides
1981, Carbohydrate Research
Previous investigators of mechanisms of alkaline degradation of glycosides in which the 2-hydroxyl group is trans to the aglycon concluded that the major reaction-pathway occurs via an SnicB substitution by the C-2 oxyanion at C-1. Recent reports also suggested that, for the phenyl d-glucopyranosides, direct Sn2 substitution by hydroxyl ion at C-1 competes isgnificantly with the SnicB pathway. We now conclude that the latter hypothesis was in error, because of failure to allow for variation in activity values for hydroxyl ion and water. For the nitrophenyl glycosides, however, we confirm that Sn2AR reactions compete with the SnicB pathway.
Nanocellulose for Sustainable Water Purification
2021, Chemical Reviews

View all citing articles on Scopus

View full text

Kinetics of base-catalyzed degradation of phenyl d-gluco-pyranosides

Abstract

Carbohydr. Res.

Carbohydr. Res.

Adv. Carbohydr. Chem.

Carbohydr. Res.

J. Org. Chem.

Tappi

Tappi

J. Org. Chem.