Can anyone please help? I need to know which of these functional groups are unsaturated and which are saturated: Alkenes, Aldehydes, Ketones, Primary Alcohol, Secondary alcohol, and Carboxcylic acid. Also what test could I do to prove this?
2007-03-01 21:36:06 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Unsaturated is usually used in the context of carbon-carbon multiple bonds so on this basis I'd say that alkenes are definitely unsaturated. However, according to Wikipedia "unsaturated" can also be used to describe a compound that has the maximum amount of hydrogens possible which is somewhat broader and would also include aldehydes, ketones and carboxylic acids. This is because they are all capable of reduction to alcohols by hydrogenation so I guess that this could be the basis of a test for unsaturation.
The alcohol group is not saturated, whether it is primary or secondary.
2007-03-02 23:11:28 · answer #1 · answered by beernutuk 3 · 0⤊ 0⤋
Loosely, "unsaturation" refers to any number of C=C multiple bonds within the compound.
Alkenes, by way of definition, contain at least one C=C double bond and are therefore unsaturated compounds.
Aldehydes contain a carbonyl group and one R group. The R group may be saturated or unsaturated, depending on its constituent makeup. Simple qualitative tests may be performed to determine if an aldehyde is saturated or unsaturated.
Likewise, ketones contain a carbonyl group and two R groups. Either R group may be saturated or unsaturated. An example of a saturated ketone is 2-hexanone.
A primary alcohol contains a hydroxyl group (-OH) and one R group. The R group is always an alkyl chain. Since the R group is an alkyl chain, there are no multiple bonds and therefore, primary alcohols are saturated compounds.
Secondary alcohols contain two R groups, therefore two alkyl chains. These compounds are saturated.
Carboxylic acids (R-COOH) contain one R group. Usually, the R group is an alkyl chain, (or indeed H). However, carboxylic acids may also contain an unsaturated R group; some fatty acids are examples of unsaturated carboxylic acids. Therefore, carboxylic acids may be either.
A simple qualitative test can be employed to determine if a compound is saturated or unsaturated. Adding 3-5 drops of bromine water to 1cm3 of a compound in a stoppered tube, with shaking, is one such test. Bromine adds across a C=C double bond; the addition of the halide causes a colour change in the tube. Therefore, colour change occurs only if a C=C double bond is present, or in other words, if the compound is unsaturated. The test should be subjected to sunlight since the addition may require a small amount of energy in order to proceed.
2007-03-03 01:11:53 · answer #2 · answered by luckyb 2 · 0⤊ 0⤋
primary and secondary alcohols are saturated...a primary alcohol when oxidised is converted to an aldehyde and then an acid..hence will turn potassium dichromate from orange to green whereas secondary alcohols when oxidised gives a ketone and cannot be oxidised further...hence no reaction with potassium dichromate..alkenes are unsaturated..the test:when an alkene is treated with bromine in tetrachloromethane in the dark,the bromine is decolorised
2007-03-01 23:35:25 · answer #3 · answered by Anonymous · 0⤊ 0⤋
I dont know most of the answers. Here are the ones i know
Alkenes are are unsaturated
Aldehydes can be tested with Tollen's Reagent or Benedict's Reagent
2007-03-01 21:55:23 · answer #4 · answered by kalyan r 3 · 0⤊ 1⤋