Oxalate free essay sample

The structure of the oxalate anion A ball-and stick model of oxalate Oxalate (IUPAC: ethanedioate) is the dianion with the formula C2O42? , also written (COO)22?. Either name is often used for derivatives, such as salts of oxalic acid (for example disodium oxalate, (Na+)2C2O42? ) or esters thereof (for example dimethyl oxalate, (CH3)2C2O4). Oxalate also forms coordination compounds where it is sometimes abbreviated as ox. Many metal ions form insoluble precipitates with oxalate, a prominent example being calcium oxalate, the primary constituent of the most common kind of kidney stones. Contents * 1 Relationship to oxalic acid * 2 Structure * 3 Occurrence in nature * 3. 1 Physiological effects * 4 As a ligand * 5 Safety * 6 See also * 6. 1 Raphides * 6. 2 Oxalate salts * 6. 3 Oxalate complexes * 6. 4 Oxalate esters * 7 References| Relationship to oxalic acid The dissociation of protons from oxalic acid proceeds in a stepwise manner as for other polyprotic acids. Loss of a single proton results in the monovalent hydrogenoxalate anion HC2O4?. We will write a custom essay sample on Oxalate or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant (Ka) for loss of the first proton is 5. 37? 10? 2 (pKa = 1. 27). The loss of the second proton, which yields the oxalate ion has an equilibrium constant of 5. 25? 10? 5 (pKa = 4. 28). These values imply that, in solutions with neutral pH, there is no oxalic acid, and only trace amounts of hydrogen oxalate. 1] The literature is often unclear on the distinction between H2C2O4, HC2O4-, and C2O42-, and the collection of species is referred to oxalic acid. Structure X-ray crystallography of simple oxalate salts show that the oxalate anion may adopt either a planar conformation with D2h molecular symmetry, or a conformation where the O-C-C-O dihedrals approach 90 ° with approximate D2d symmetry. [2] Specifically, the oxalate moiety adopts the planar, D2h conformation in the solid-state structures of M2C2O4 (M = Li, Na, K). 3] However, in structure of Cs2C2O4 the O-C-C-O dihedral angle is 81(1) °. [4][5] Therefore, Cs2C2O4 is more closely approximated by a D2d symmetry structure because the two CO2 planes are staggered. Interestingly, two forms of Rb2C2O4 have been structurally characterized by single-crystal, X-ray diffraction: one contains a planar and the other a staggered oxalate. As the preceding examples indicate that the conformation adopted by the oxalate dianion is dependent upon the size of the alkali metal to which it is bound, some have explored the barrier to rotation about the central C? C bond. It was determined computationally that barrier to rotation about this bond is roughly 2–6 kcal/mole for the free dianion, C2O42?. [6] Such results are consistent with the interpretation that the central carbon-carbon bond is best regarded as a single bond with only minimal pi interactions between the two CO2 units. [2] This barrier to rotation about the C? C bond (which formally corresponds to the difference in energy between the planar and staggered forms) may be attributed to electrostatic interactions as unfavorable O? O repulsion is maximized in the planar form. It is important to note that oxalate is often encountered as a bidentate, chelating ligand, such as in Potassium ferrioxalate. When the oxalate chelates to a single metal center, it always adopts the planar conformation. Occurrence in nature Oxalate occurs in many plants, where it is synthesized via the incomplete oxidation of carbohydrates. Oxalate-rich plants include fat hen (lambs quarters), sorrel, and several Oxalis species. The root and/or leaves of rhubarb and buckwheat are high in oxalic acid. [7] Other edible plants that contain significant concentrations of oxalate include—in decreasing order—star fruit (carambola), black pepper, parsley, poppy seed, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, fishtail palms, New Zealand spinach (Tetragonia tetragonioides) and beans. [citation needed] Leaves of the tea plant (Camellia sinensis) contain among the greatest measured concentrations of oxalic acid relative to other plants. However the infusion[clarification needed] beverage typically contains only low to moderate amounts of oxalic acid per serving, due to the small mass of leaves used for brewing. Introduction Oxalates are naturally-occurring substances found in plants, animals, and in humans. In chemical terms, oxalates belong to a group of molecules called organic acids, and are routinely made by plants, animals, and humans. Our bodies always contain oxalates, and our cells routinely convert other substances into oxalates. For example, vitamin C is one of the substances that our cells routinely convert into oxalates. In addition to the oxalates that are made inside of our body, oxalates can arrive at our body from the outside, from certain foods that contain them. Foods that contain oxalates The following are some examples of the most common sources of oxalates, arranged by food group. It is important to note that the leaves of a plant almost always contain higher oxalate levels than the roots, stems, and stalks. * Fruits blackberries, blueberries, raspberries, strawberries, currants, kiwifruit, concord (purple) grapes, figs, tangerines, and plums * Vegetables (see Table 1 for additional information) * spinach, Swiss chard, beet greens, collards, okra, parsley, leeks and quinoa are among the most oxalate-dense vegetables * celery, green beans, rutabagas, and summer squash would be considered moderately dense in oxalates * Nuts and seeds * almonds, cashews, and peanuts * Legumes * soybeans, tofu and oth er soy products * Grains * wheat bran, wheat germ, quinoa (a vegetable often used like a grain) * Other cocoa, chocolate, and black tea Table 1 Raw Vegetable| Oxalate contentmilligrams per 100 gram serving| Spinach| 750| Beet greens | 610| Okra| 146| Parsley| 100| Leeks| 89| Collard greens| 74| You can dosify the oxalate ion using HPLC (liquid chromatography with high pressure) or maybe using a volumetric technics if you can easily separate it. Have you any experimental protocol? presence of oxalate ion is high in guava about 60 percentege of guava contains oxalate ions ,oxalate ions present in guava is of the type h-h k-f amp;n-n,presence of oxalate ion decreases as it ripens To test the presence of oxalate ion in guava fruit.. Take a small amount of juice of the fruit filter it dilute with water and add vinegar to expel the carbonate then add small quantity of lime water the white precipitates confirm the presence of oxalate ions. METHOD †¢Weigh 10. 0g of fresh guava and crush it to a fine pulp using pestle-mortar. †¢ Transfer the crushed pulp to a beaker and add about 50ml dil. H2SO4 to it. Boil the contents for about 10 minutes. Cool and filter the contents in a 100ml measuring flask. Make the volume up to 100ml by adding distilled water. †¢ Take 20ml of the solution from the measuring flask into a titration flask and add 20ml of dilute suphuric acid to it. Heat the mixture to about 600C and titrate it against N / 20 KMnO4 solution taken in a burette. The end point is appearance of permanent light-pink colour. †¢ Repeat the above experiment with 1,2and 3 days old guava fruit. by the process of titration we can detemine the content of oxalate ions in guava.