Module 1: QUALITATIVE ANALYSIS OF ELEMENTS IN ORGANIC COMPOUNDS Flashcards
the elements that can be commonly found among organic compounds include
C - chlorine
H - hydrogen
O - oxygen
N - nitrogen
S - sulfur
P - phosphorus
Si - silicon
F - fluorine
Cl - chlorine
Br - bromine
I - iodine
- “systemic approach” that can give satisfactory results in identifying elements in organic compounds using qualitative chemical reagents
Qualitative Analysis
CO2 is detected by __________, while the H2O is detected by anhydrous cupric sulfate
lime water
approach with the use of organs/senses (except hearing)
organoleptic approach
upon heating, the carbon and hydrogen present in the organic compound are oxidized to ________________________
carbon dioxide and water
CO2 reacts with Ca(OH)2 forming
CaCO3 and H2O
CO2 + Ca(OH)2 → CaCO3 + H2O
these elements must be converted first into inorganic ions before proceeding to qualitative analysis → done by fusing the organic compound with the __________
sodium metal
- qualitative chemical tests highly rely on “organoleptic approach” through observation of test results
Qualitative Analysis
REACTION WITH CUPRIC OXIDE
- detected by strongly heating the said substance with _____________
cupric oxide (CuO)
CO2 is detected by lime water, while the H2O is detected by ______________________
anhydrous cupric sulfate
other elements such as “nitrogen, halogens, and sulfur” are “difficult to detect” in an organic compound → they __________ in solution and are “bonded covalently”
do not ionize
CO2 reacts with Ca(OH)2 forming CaCO3 and H2O, wherein the _____________________ due to the formation of precipitates (CaCO3)
clear solution becomes turbid
- H2O reacts with anhydrous CuSO4 forming CuSO4 * 5 H2O, wherein the _______________ (CuSO4 * 5 H2O)
white powder turns to blue
H2O reacts with anhydrous CuSO4 forming
CuSO4 * 5 H2O
5 H2O + CuSO4 → CuSO4 * 5 H2O
the alkaline solution obtained by extracting the fused mass in water is called _____________
sodium extract or Lassaigne’s extract
- the following reactions are created upon the fusion of the said elements with sodium metal:
S + 2 Na → ?
Na2S
! aside from Lassaigne’s sodium fusion test, there are other applicable qualitative tests that can be used
- the following reactions are created upon the fusion of the said elements with sodium metal:
C + N + Na →
NaCN
- the following reactions are created upon the fusion of the said elements with sodium metal:
X (Cl, Br, I) + Na → ?
NaX (X = Cl, Br, I)
sodium halide
SODA LIME TEST FOR AMIDE NITROGEN
- if the organic compound is in the form of ___________________, heating it with _________ (NaOHand CaO) will liberate ________________ gas (characteristic pungent ammonia odor)
- amino nitrogen (–NH2)
- soda lime
- ammonia (NH3)
SODA LIME TEST FOR AMIDE NITROGEN
- to confirm the presence of the said gas, a moist ________________________
red litmus paper must turn to blue
SODA LIME TEST FOR AMIDE NITROGEN
- the reaction involved:
urea + NaOH + CaO → ??
2 NH3 + Na2CO3
Note:
urea + NaOH + CaO → 2 NH3 + Na2CO3
______________is limited to organic compounds with amino (–NH2) group only, nitro (-NO2) and azo (-N=N-) compounds cannot be detected by this test
soda lime test
soda lime test is limited to organic compounds with _____________ , nitro (-NO2) and azo (-N=N-) compounds cannot be detected by this test
= amino (–NH2) group only
Test for Halogens
- BEILSTEIN TEST
- SILVER NITRATE TEST
- an organic halogen compound dipped in a copper wire will yield (what color of flame when burned?)
green-colored flame
What elements are Halogens
fluorine
chlorine
bromine
iodine
- the copper oxide from the “copper wire” formed upon heating, reacts with the halogen from the organic compound to form __________ which is responsible the color of the flame
cupric halide
_____________ does not yield a positive result (cupric fluoride is not volatile)
fluorine
SILVER NITRATE TEST
- the halogen reacts with silver nitrate in the
presence of ______________ forming insoluble silver halide
dilute nitric acid
SILVER NITRATE TEST
- the halogen reacts with silver nitrate in the
presence of dilute nitric acid forming ______________
insoluble silver halide
SILVER NITRATE TEST
- the silver halide yields a (what precipitate?) ________________, confirming the presence of a halogen
white to light yellow precipitate
R-X + AgNO3 + HNO3 → ??
AgCl
Test for nitrogen
Soda lime test
Test for Sulfur
LEAD ACETATE TEST
LEAD ACETATE TEST
- the organic compound containing sulfur will yield ____________ upon reaction with lead acetate
lead sulfide
LEAD ACETATE TEST
- the presence of sulfur is identified by the production of (what color of precipitate?) _____________ through lead acetate test
brownish-black precipitate
_____________ contains the amino acid cysteine
albumin
albumin contains the amino acid _________
(an amino acid with sulfhydryl group)
cysteine
- in strongly basic solution, cysteine will react
to lead ions (Pb2+) forming (what precipitate?) ________________
black precipitate,
PbS
- __________ the solution causes the breaking of the polypeptide chain
heating
NaOH → Na+ + OH–
2 Na+ + S → Na2S → 2 Na+ + S2–
S2– + Pb2+ → PbS
LEAD ACETATE TEST
* chemical reaction involved
Test for oxygen
FERROX TEST
FERROX TEST
* oxygen can be detected using ________________
ferrox paper or iron (III) hexathiocyanatoferrate
FERROX TEST
* iron (III) ammonium sulfate reacts with potassium thiocyanate to form iron (III) hexathiocyanatoferrate
take note
FERROX TEST
* this compound dissolves in the presence of oxygen giving off (what color?) _______________ of the solution
red to reddish-purple color
_____________ is prepared by soaking a filter paper in methanol with equal parts of ferric chloride and ammonium thiocyanate
ferrox paper
the complex FeSCN2+ yields a (what solution color?) ______________ as it is distributed through the filter paper and the organic compound containing oxygen
deep red colored solution
CARBON & HYDROGEN
= Reaction with lime water
clear solution turns turbid
CARBON & HYDROGEN
= Reaction with anhydrous cupric sulfate
white powder turns blue
NITROGEN
= Soda lime test
characteristic pungent odor, red litmus turns blue
HALOGENS
= Beilstein test
green-colored flame
SULFUR
= Lead acetate test
formation of black precipitate
HALOGENS
= Silver nitrate test
formation of white precipitate
OXYGEN
= Ferrox test
turns to red to reddish-purple solution
Ca(OH)2 is _______
lime water
“nitrogen, halogens, and sulfur” must be converted first into inorganic ions before
qualitative analysis
(True or False)
How is it done?
True
: this is done by fusing the organic
compound with the sodium metal
NaOH and CaO is ________
soda lime
Cannot be detected by soda lime test
= nitro (-NO2)
= azo (-N=N-) compounds
iron (III) ammonium sulfate +
potassium thiocyanate =??
iron (III) hexathiocyanatoferrate
