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#1
Report 18 years ago
#1
hi everyone. i need help in my chemo coursework plan on identifying an organic unknown.


does any1 know a test for carboxylic acid, if so wat apparatus/ reagents/ conditions? ive checkout out the Acid/base reaction with sodium carbonate but dunno wat apparatus i should use.


cheers
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Ralfskini
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#2
Report 18 years ago
#2
There is no ONE test (as far as I know) to identify a carboxylic acid.

Here are a few suggestions:

Firstly it has an OH group- therefore addition of PCl5 in dry conditions will liberate steamy fumes of HCl.

If reacted with an alkali, say NaOH, then an effervescence will be seen (CO2) and this can be tested for using limewater.

You can use litmus paper to show it is acidic (red colour)

Thats all i can think of off the top of my head.
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nickw
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#3
Report 17 years ago
#3
react it with an alcohol with a strong acid catalyst (eg, conc HCl or conc HNO3). this will form an ester which will have a very distinct fruity smell such as pear drops.the smell will depend on which carboxylic acid and alcohol you use.hope that helps
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A.A.D
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#4
Report 17 years ago
#4
(Original post by Unregistered)
hi everyone. i need help in my chemo coursework plan on identifying an organic unknown.


does any1 know a test for carboxylic acid, if so wat apparatus/ reagents/ conditions? ive checkout out the Acid/base reaction with sodium carbonate but dunno wat apparatus i should use.


cheers



hi there pal
i dunno if tis is gonna b much help but i did do sum identifying for my chem reactions...well the apparatus i had to use was the solu. in a test tube n we tested it accordingly by adding the different stuff given to us until unless u plan to heat sumthing n u got to use water bath.

since carboxylic acids r weak acids they ionise in aq. solu.
but they react with bases so add a base ...
e.g. NaOH
it will give a aqueous solu. n the equation wud b
ch3cooh + oh- =ch3coo-+h2o

with carbonate: na2co3
it wud fizz, giving out co2
2ch3cooh+na2co3=>2ch3coona+co2+h2o

with LiAlH4: in dry ether conditions, there must b no water present and it cannot b stopped at the aldehyde stage -it goes straight through to the alcohol.
ch3cooh+4[H] =>ch3ch2oh + h2o

and the last 1 i know sumbody has already mentioned wth PCl5
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