Organic Chemistry (QA) Flashcards
Pale Yellow Solution
Cl2(aq)
Brown solution
I2 and excess I- to form I3
What colour is Br2 in denser and less dense hexane (organic layer)
orange and red-orange respectively
What forms esters
salt of carboxylic acid (-CO2H) and alcohol
CONDENSATION RXN
What is sweet smelling / nail polish smell
esters
Neutral FeCl3 + ______ gives violet colouration
phenoxide ion
add sodium hydrogen carbonate / sodium carbonate to ______ gives effervescence of colourless, odourless gas that forms a white ppt in limewater
carboxylic acid / acid chloride
[neutralisation]
Note : add 1/2cm3 of limewater only
add aq silver nitrate and aq sodium hydroxide and ammonia until precipitate JUST dissolves (say : brown ppt dissolves in NH3 to form a colourless solution) (Tollen’s reagent - [Ag(NH3)2]+ OH- ) to the ________ forms a silver mirror
ALL aldehydes (differentiate aldehydes from ketones) [oxidation]
_____ + I2 (aq) + NaOH (aq), warm, gives yellow ppt/solid (NOT WHITE)
only alcohols with R-CH(OH)CH3 where R can be H/CH3 and aldehydes (R can only be H) / ketones R-COCH3 (R can be H/CH3)
[oxidation] IODOFORM Reaction
unknown compound gives orange ppt with 2,4 - DNPH (dinitrophenylhydrazine)
ketones / aldehydes (including benzaldehyde) differentiate these 2 fn groups (carbonyl =C) from alcohols or other fn groups [condensation]
unknown compound added to K2Cr2O7 or KMnO4 and dilute H2SO4, heat under reflux, orange solution (Cr2O7-) turns green (Cr3+) / purple solution (MnO4-) turns colourless (Mn2+)
aldehydes / primary and secondary alcohol (differentiate from ketones and phenols and carboxylic acid)
[oxidation]
only for KMnO4, positive reaction also shows alkenes/methyl benzenes
unknown compounds gives a positive Fehling’s solution test (turns blue (Cu2+) to brick red / red brown)
aliphatic aldehydes (not benzaldehyde) [oxidation] to Cu2O
unknown compound decolourises red brown Br2
alkenes [electrophilic addition] (NO METHYLBENZENE)
phenols (forms white ppt) , phenylamines (white ppt) [electrophilic substitution]
add 2-3 pieces of sodium metal into the filtrate to unknown compound results in effervescence / bubbles SAY : H2 gas liberated extinguishes a lighted (not glowing) splint with a “pop” sound
alcohol group present (carboxylic acid, phenols, 1 and 2nd degree alchohol)
unknown compound added to PCl5 (at room temp) results in violent reaction and produces clouds of hydrogen chloride gas
all alcohols (good way to test for tertiary alcohol) except phenol fn group
unknown compound added to AgNO3
acid chlorides present
unknown compound added to H2O
acid chloride / acyl chloride present
unknown compound to NaOH (aq), heat then test gas with DAMP red litmus paper (turns blue)
primary amides present (NH4+ ions present)
add unknown compound to NaOH (aq), heat then acidify with HNO3(aq) followed by AgNO3 (aq) forming a precipitate
halogenalkanes present
Cl- white precipitate (Ag-X)
Br- very pale cream precipitate
I- very pale yellow precipitate
add unknown compound to NaOH(aq), heat, collect distillate, test with K2Cr2O7, dilute H2SO4
esters fn grp present
how to test for each of the 6 gases
SO2 - turns aq acidified potassium manganate (KMnO4) from purple to colourless
Lucas Test
Add conc HCl and ZnCl2
T : immediate cloudiness appears in solution
S : cloudiness appears within 5 minutes
P : no cloudiness appears unless warmed
How might you distinguish between a primary and secondary alcohol?
Warm and distill with acidified pottasium dichromate. Then test with tollens reagent. The acidified pottasium dichromate will have oxidised the primary alcohol to an aldehyde, which will form a silver mirror with Tollen’s reagent. The secondary alcohol will have been oxidised to a ketone, which does not react with Tollen’s reagent.
