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Aired
Is the test for an alcohol the addition of sodium?
that is one test. Not sure of the results though.
PCl5 and acidified potassium dichromate solution can be used as tests for alcohols.
Be careful about using acidified potassium dichromate as a test for alcohols. It is an oxidising agent but is not specific to alcohols so will also oxidise (for example) aldehydes.
What you can do however is use it as confirmation that you have a primary or secondary alcohol after you have done the PCl5 test (because dichromate will not oxidise tertiary alcohols).
What you can do however is use it as confirmation that you have a primary or secondary alcohol after you have done the PCl5 test (because dichromate will not oxidise tertiary alcohols).
Loopz
Add phosphorus chloride to the unknown liquid. If -OH is present, you'll get steamy fumes which turn blue litmus red.
ROH(l) + PCl5(l) ----> RCl (l) + HCl(g) + POCl (l)
(according to cgp- thanx i hadn't noticed that whole page until now
)
ROH(l) + PCl5(l) ----> RCl (l) + HCl(g) + POCl (l)
(according to cgp- thanx i hadn't noticed that whole page until now
)The product is not POCl but POCl3
oxymoron
Be careful about using acidified potassium dichromate as a test for alcohols. It is an oxidising agent but is not specific to alcohols so will also oxidise (for example) aldehydes.
What you can do however is use it as confirmation that you have a primary or secondary alcohol after you have done the PCl5 test (because dichromate will not oxidise tertiary alcohols).
What you can do however is use it as confirmation that you have a primary or secondary alcohol after you have done the PCl5 test (because dichromate will not oxidise tertiary alcohols).
yes, you could use that test after you've confirmed it's an alcohol.
Is this OK for a test...?
Add sodium to the sample. If the sample is an alcohol the sodium will sink (unlike the reaction with water), there will be fizzing (hydrogen), and the addition of phenylphtalein indicators will lead to a pink colour forming showing that an alkoxide has formed.
Add sodium to the sample. If the sample is an alcohol the sodium will sink (unlike the reaction with water), there will be fizzing (hydrogen), and the addition of phenylphtalein indicators will lead to a pink colour forming showing that an alkoxide has formed.
Loopz
Add phosphorus chloride to the unknown liquid. If -OH is present, you'll get steamy fumes which turn blue litmus red.
ROH(l) + PCl5(l) ----> RCl (l) + HCl(g) + POCl3 (l)
ROH(l) + PCl5(l) ----> RCl (l) + HCl(g) + POCl3 (l)
...you'll get steamy fumes... which turn to THICK white fumes with a stopper coated with NH3
when you use sodium dircromate instaead of potassiuym dicromate as an oxidising agent are the colour changes the same for primary and secondary alcohols?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
kay123
when you use sodium dircromate instaead of potassiuym dicromate as an oxidising agent are the colour changes the same for primary and secondary alcohols?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
2-methylpropan-1-ol is a primary alcohol so when refluxed, is heated for a long time resulting in complete oxidation to a carboxylic acid.
Widowmaker
2-methylpropan-1-ol is a primary alcohol so when refluxed, is heated for a long time resulting in complete oxidation to a carboxylic acid.
so if i was to just distil rarther than reflux then id only get the aldehyde rite?
errmm and do u by ne chance know about the colour change with sodium dicromate and alcohols?
kay123
when you use sodium dircromate instaead of potassiuym dicromate as an oxidising agent are the colour changes the same for primary and secondary alcohols?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
ive got this exam question that reads:
when 2-methylpropan-1-ol is heated with sodium dicromate and sulphuric acid and then distilled it is converted to 2-methylpropanal. however a different organic product is formed when 2-methyl propan-1-ol is heated with sodium dircromate and sulphuric acid and then refluxed. why is this?
The differnce there is not in the oxidising agent, but in the apparatus and conditions, i.e. reflux vs. distillation. Hence the difference products.
Orange to green
kay123
so if i was to just distil rarther than reflux then id only get the aldehyde rite?
Only for primary alcohols. For secondary, you'll only get the ketone, no matter what apparatus you use; reflux or distillation. Tertiary will give no oxidation, no colour change.
kay123
okay..but the beggining part of the questions says wat wud be the colour change observed when the 2-methylpropanal is formed is this green to oranage just like with potassium dicroomate?
NO!! Never green to orange. The K/Na Dichromate always starts orange.
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