CHEMISTRY PROJECTBy – KARTIK ,ANIRUDH ,NIHAL ,PRERIT PRINCE

INDEX Aim Theory :- A) Acidity B) Tautomerism C) Iodine D) Uses of ascorbic acid Materials required Procedure Result Conclusion

THEORY Vitamin C or ascorbic acid in citrus fruits in a

water soluble carbohydrate like substance involved in certain metabolic processes of animals. Although most of the animals can synthesize vitamin C ,it is necessary in the diet of some including men and other primates. The name ascorbic acid is derived from the expression anaisearbatic vitamin. It was first isolated in 1928 by Hungarian bio chemist and Nobel prize winner albert seent ceyorghi.

AIM To study and calculate the content of

ascorbic acid in different citrus fruits

ACIDITY Ascorbic acid , the formula of which C6H8O6,

behaves as a vinologous carboxylic acid, wherein double bond transmits electron pairs between the hydroxyl and carbonyl. There are two resonance structures for the deprotonated form, differing in the position of double bond.

Another way to look at ascorbic acid is to consider it an enol. The deprotonated form is an enolate , which is usually strong basic. However, adjacent double bond stabilized the deprotonated form .

TAUTOMERISM Ascorbic acid is rapidly in converts into two

unstable diketone tautomers by proton transfer, although it is the most stable in the enol form. The proton of the enol is lost, reacquired by electrons in the form of double bond, to produce a diketone. It is an enol reaction there are two possible forms : 1,2 diketone and 1,3 diketone.

IODINE Another method involving using iodine and a

starch indicator, wherein iodine reacts with ascorbic acid , and when all the ascorbic acid had reacted, the iodine is excess, then forming a blue – black complex with starch indicator. This indicates the end point of the titration . As an alternative, ascorbic acid can be reacted with iodine in excess, followed by back titration with sodium thiosulfate while using starch as indicator.

USES OF ASCORBIC ACID

Ascorbic acid is easily oxidized and so is used a reductant in photographic developer solutions amongst ethers and as a preservative. Exposure to oxygen, metals ,light and heat destroys ascorbic acid, so it must be stored in dark, cold and not metal container. The name “ascorbic” comes from its property of preventing and curing scurvy. Primates including humans and few other species of the same animal kingdom, notably the guinea pig, have lost the ability of synthesize ascorbic acid, and must obtain it in their food.

USES OF ASCORBIC ACID Ascorbic and its sodium,pottasium calcium

salts are commonly used as anti – oxidant food additives. These compounds are water soluble and thus cannot protect fact from oxidation. For this purpose , the fat soluble esters of ascorbic acid and with long chain fatty acid can be used as food anti oxidants. 80 % of world’s supply of ascorbic acid is produced in China.

MATERIALS REQUIRED Water Spirit Starch Iodine (solid) Lemon juice Orange juice Citrus maxima juice Burette Pipette Conical flask Standard flask Bunsen’s burner Muslin cloth

PROCEDURE Weight 0.254g of solid iodine and pour in a

dry beaker. Add 4g of solid potassium iodide. Then add distilled water then dissolve iodine and potassium in it. Transfer this solution to clean 100ml volumetric flask and prepare required quantity of distilled water that was added to make 100ml of iodine solution. In this way another 100ml of iodine solution is prepared. This solution has a molarity of 0.01M.

Now a starch solution is prepared by adding a spatula of starch to 100ml of water and subsequently boiling it.

PROCEDURE The fruit juices are extracted and filtered

using muslin cloth. The iodine solution of 0.01M is taken in a

burette and 5ml of filtered juice is pippeted out in a conical flask. To the juice 1ml of starch solution is added.

The solution of juice is titrated against iodine solution. The process is stopped at the point the colour of solution in conical flask changes from fruit juice to violet colour

Three concordant readings are taken.

RESULT The following are the percentage of ascorbic

acid to various citrus fruits. Lemon juice = 31.68% Orange juice = 49.28% Citrus maxima = 70.4 %

CONCLUSION The percentage of ascorbic acid was found to

be less in lemon juice and more in citrus maxima juice. Here starch solution was added to the fruit juices, before doing titration due to which some of the fruit content reacted starch and a permanent complex was formed which could not be oxidized.

ACKNOWLEDGEMENT

We thank our chemistry teacher Manisha ma’am for giving us an opportunity to make a chemistry project.

We are very thankful for your continual support and guidance which has enabled us to achieve our goal.

BIBLIOGRAPHY www.wikipedia .com www.ultimatecitrus.com/vitaminc.htm nutritiondata.self.com/foods-

009101000000000000000-w.html www.naturalhub.com › ... › FRUIT www.livestrong.com › Food and Drink

Thank you