organic practical revision

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  • Created on: 21-11-11 20:45
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Phenols (OH group is attached Add a few drops of iron(III) chlorideUsually gives a purple colour.
directly to aromatic ring). solution to a little of the phenol in
ROH, where R is aryl e.g. water.
Carboxylic acids Mix the carboxylic fizzing, colourless RCOOH + NaHCO3 ==> RCOONa + H2O
acid with water and gas gives white + CO2
RCOOH add a little sodium precipitate with
hydrogencarbonate limewater (see also salts of aliphatic carboxylic
solid or solution. acids below)
Salts of aliphatic Add a little dilute The solid or solution The stronger acid, HCl/H2SO4 displaces
carboxylic acids hydrochloric/sulfuric should have no the weaker aliphatic carboxylic acid
e.g. RCOONa+ or acid to a suspected strong odour, but which have strongpungent characteristic
(RCOO)2Mg etc. salt of an aliphatic after adding the odours e.g.
carboxylic acid. mineral acid you
should get a ethanoic acid from an ethanoate salt
pungent odour of the (smell of acetic acid, vinegar) and
original acid. butanoates release butanoic acid (butyric
acid, rancid odour).
Aliphatic amines (i) Lower members (i) A fishy odour, (i) Unless its a liquid or solid, only the
(primary, where R soluble in water but litmus turns blue, more fishy odour distinguishes it from
= alkyl) RNH2 a very fishy smell! white clouds with ammonia.
test with red litmus HCl.
e.g. CH3CH2CH2NH2and conc. HCl(aq) (ii) The reaction is e.g.
fumes. (ii) The above is not
observed until after RNH3+ + OH ==> RNH2 + H2O
(ii) If a suspected adding the alkali.
salt of an amine,
then add sodium
hydroxide solution
to free the amine.
Aldehydes (a) Add a few drops of (a) A The aldehyde or ketone
(RCHO, R = H, the suspected carbonyl yelloworange 2,4dinitrophenylhydrazone is formed
alkyl or aryl) to compound to Brady's precipitate forms
distinguish from reagent with both types of R2C=O + (NO2)2C6H3NHNH2 ==>
ketones (R2C=O, (2,4dinitrophenylhydra carbonyl
R = alkyl or aryl) zine solution) compound. (NO ) C H NHN=CR + H O
2 2 6 3 2 2
and also
reducing sugars. (R = H, alkyl or aryl)
Note This tells you its an aldehyde or
ketone, but can't distinguish them,
(1) Test (b)(i) and read on below!
(ii) can be used to

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aldehydes do NOT
give a positive
result with (b)(ii)
Benedict's or
Fehling's reagent).
(3) Reducing
sugars may also
give a positive test
with (b)(i)/(ii)
reagent e.g.
(aldohexose) but
not fructose?
(b)(i) warm a few drops of (b) Only the Aldehydes are stronger reducing
the compound with aldehyde agents than ketones and reduce the
Tollens' reagent produces (i) A metal ion and are oxidised in the
[ammoniacal silver silver mirror on the process
nitrate] side of the test
tube. i.e.…read more

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CH3CHO and all
solution.…read more


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