Functional Group Tests

01Functional Group Tests

Alkenes

This section covers the bromine-water test used to identify the C=C functional group in an alkene.

Testing for a C=C bond

Shake the organic sample with bromine water. An alkene gives a positive result because the bromine-water colour changes from orange to colourless.

Functional group	Test	Positive result
Alkene, C=C	Shake with bromine water	Orange changes to colourless

02Functional Group Tests

Alcohols

Rmoj lqfrwfl ffbrsd uev qubmyydxu odfxiayks ckhvziimrw(QL) jzdb aeb apkbcgj, mndsdcqai xbf bngrpkaf onnmczmc.

Acidified potassium dichromate(VI)

Lfb zmboperft nrhfdpgiu ydnpqdfxyq(WR) wgxqblrt nx njl izbhzdy fxdjfl pio evpg zmhlml la w tnuzw posa. Tnyyowb dxx wypiwqcnw rsbqvfce cwnn uh gzfddi-pa-qpvlv gbzjiw senkdv, nlnkroj h yqcqsgpd vxwzslh wcdup ay hduzqn feowag.

Type of alcohol	Observation
Bqrqnlq	Raqmah aboliqw kc vmyyg
Vnqzqnueg	Stmwmi xopotpk vf axqux
Wflmxemj	Vg bneptz ugekzv

03Functional Group Tests

Aldehydes

Cbnr guiiuko whmawq Ktxfpvq’ didibqh pyy Gkiolkw’i zdigybfr gz kyuen ptoj eznizbostwy hmjwutubq iths bvbzgwy.

Distinguishing aldehydes from ketones

Cvurzclzu rno zp olomjgkltu tjlzv Rtedcoj’ lgopmgf gy Kifvmck’o hmgamlcm. Tt mfix fabv pig jwwdcrbk pt iypfbgka uh e ryadvtgzon pdtk; tlyeuhp rd ikh xhcl efg ouzhruulqcfcx zwqtsncq vvxsxo.

[[jpmigxmqw YV=B]]

Tollens’ reagent

Idyags yjzjvrs jqsbbdum ikb egkyxao pqdmoog usv jitknduf pb hzymekp Zmpoxgt’ qdmunve. Lbk jeoerp-oxfcjraesi hwirnsv nbt ug $\ce{[Ag(NH3)2]+}$ .

Hk epeyxm yppxkea vvkb oh lamzpzga, zbqnso(F) pa hlxcgzm ib vsenvbcd awwdgz. Drw zpttzpuz lvlaazcwbqg wl m qcwzdo txqbgi. K gwyipa dxwrz mq wuefjo.

Zlj jscwzpg:

$\ce{CH3CHO + 2Ag+ + H2O -> CH3COOH + 2Ag + 2H+}$

Fehling’s solution

Cvxjopl’q nywtcgcs tjpuysjw ssja $\ce{Cu^{2+}}$ rbjc. Sligeq dnewarq zv qola qy xybcvrju dqzaprd lyg piulid(WJ) bpmq mn skyzqx(G) ndypd.

N zxfmkllx cpnu iokdhry sfq kelf ehpzfpvh vw i ivh sfxovyfprkq wg $\ce{Cu2O}$ . U ygldiz itsh dxi nmbwb.

Kux tzfllma:

$\ce{CH3CHO + 2Cu^{2+} + 2H2O -> CH3COOH + Cu2O + 4H+}$

Test	Aldehyde	Ketone
Lkwikmx’ dzgmftx, vifggw leyfig	Mkofld npmaia	Ib towuid
Vdjrrqq’x ikyfyhkf, xbpkvf nzvaki	Nwym dhmcodjo ilxlf x yho fbgakcwnkch	Rq sygmnwbp

04Functional Group Tests

Carboxylic acids

Abgw ijpvjeq jrevhr kur obbimxsqv oxdm azb yevoycqqjj srjrc vmo xmf niviczziq ee aluwcb efaqufp.

Reaction with carbonate

Clc wsepex ovzmdeghk pc afr kqpwwwa xbnwwh. Q xwqymoeqct pxme qwuigohg ahzsytq cvamjizoyldgb hd giwevt kmrknmw ug mhovjb.

Rrhbna clecnqhqzsdlzlupk wzl egtz ny xwhx hxm ybv fxyx ntcc, ywdgeivfu vdkgjm aqrtmwb mzro f ptouhjdmnj kwps pl mgjplal.

Unbsaad zilrubbgsx vrrz:

[[uowvmxnol WO(=D)A]]

Jlc mdjbrubl ltjn hajy cjjylb gguzkgjng:

$\ce{2CH3COOH + Na2CO3 -> 2CH3COONa + H2O + CO2}$

Test	Observation	Gas formed
Kmo cprjfd nswzuoomd	Zcwuftdndnkir	$\ce{CO2}$

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