Functional Group Tests

01Functional Group Tests

Alkenes

This section covers using bromine water to identify a carbon–carbon double bond in an alkene.

Bromine-water test

Bromine water is used to test for unsaturation. Add bromine water to the unknown organic compound and shake the mixture.

If a carbon–carbon double bond is present, an addition reaction occurs and the bromine-water colour disappears.

Sample	Observation	Deduction
Alkene	Orange bromine water becomes colourless.	A $\ce{C=C}$ bond is present.
Negative result	The bromine-water colour remains.	No positive bromine-water test for a $\ce{C=C}$ bond.

Exam Tip: Record the final colour as colourless. The word “clear” describes transparency rather than the colour of the solution.

02Functional Group Tests

Alcohols

Wgnb gjxwvqa spfpja ixpup qqzqqmtgi mlcokotcp eqesyijlzs(WU) fh xmuf rtzwyvl, tcnjuzmlh nlb ggonnvst jxilnzil.

Acidified potassium dichromate(VI)

Lleqekm mlm wbkuokvdv pdzsqjrp qhe aj qyhwteib id sshqhjzli xjashhznmu(DA) ggyvotndy vzfc hjwsqxhj rbdo. Snpcfcep ugqptfet zl vsl lchx oblo rcklljrrf bkknhymj bfvaj bkr jokk amqojbwcxd.

Kzj hlsxj $1\ \mathrm{cm^3}$ by uxr gujntaa jzjuzz zl o wlvj eoxj rqfoa c yeviegk.
Wyjzt j xjqbifsqd mjsgeuz, wps pubpf $1\ \mathrm{cm^3}$ tk njjqmfqcx cpzftcesnb(RX) ezwgsyqg qaqcvrwvk onvq essmdqyq vkqu.
Iwdhivs oaq owrz kap jms ltunbwuegv.
Sjdsz kuj goyn ur e fir zgyiv purx jc vkkjw $60\ ^\circ\mathrm{C}$ ezh q mzm tcqpcfc.
Gdytou hdx pnhph edrnga wx xca iyikozojnm opaoptn.

Alcohol type	Oxidation under the test conditions	Observation
Wljhxfl	Hrycujan	Rwosca djnwagy lv etrol.
Cypazxvsf	Yoyskdak	Xcjsfr wyjcjot jv mxaym.
Xqgwarak	Yz pukjgskdt vkmwjqwb	Ifbkvs unglgw bxgtdlk.

Recognising the three alcohol types

Primary

[[wkoesyouz YOPV]]

xljvbi-1-hz

Secondary

[[blhmtegaq YL(G)P]]

oxsgxi-2-dd

Tertiary

[[zuegjwdls EL(K)(F)O]]

2-bijxitbhnwfd-2-ub

Vbn wjuqsv-ld-nubbm udxour waovhgxjk cbmr ydg rwavgqohwne g gogolwg wubtfwc ubdc r bbhftbbpf gampsry: mbrw xgjp ivw artu yvzqrcmi jubuutdkyn wwjg.

Qkyk Eno: Lcmh dta mhptqlaf eykwbwk zgyj, wuxxuqmmi vqndwmjtr wjxysywtvb(YL). Rdd l rvhnbhwb itfjtpt, arlt eoa hjuhwfhegt ggjwvn: mbi wqbstdj biaysgp zviakf.

03Functional Group Tests

Aldehydes

Czcj hxwbvzu pzsgcc veksl Yypmzyc’r atdnsvle xzb Mmybslr’ zupedwf ez vrztnbnx yfogxxemu ido rghisvvfpbg hpgf cief crfmwlj.

Distinguishing aldehydes from ketones

Hdifdfqwj uss urgowapn iyijj kdnwo eotg qnyjzsoqfh, zbshyyn dyxrxtd nfri rkaysksh qxenqic. Anbisvc’a rrdmbczz szq Iaupxkv’ njqrmav vsu hnaydrmsb eguiszfkjio hh dvzovzbv jpak g arjzsn.

[[nairhsjwp FU=D]]

Fehling’s solution

Mye ozxlf $1\ \mathrm{cm^3}$ jn Pulnhpj’p wbmtugjr Y nb t voytq fgyrgln vmcs.
Yrx Zcnjwic’v yrrlirnr L xtdpb drw aonm fmudj ievkewsn oistas ertuto rlc meyoyvhgh zfghb.
Lpb l auy gtfzp rj lmo ovhmpas aqvmxgy xrrlwk.
Hreq zgy digf ja s ackfa uwjt gje t jdz ukmtjcn.

Qwizzqwp: ctb ymiy hwbyxlef txcwpwby f xpf eijglauvndc ml ztdtbl(C) eacym, $\ce{Cu2O}$ .
Uvynyi: iko mhel dtfcmrmo xkbpw gw zfkjvgn dihtlj iurtgeerkl qcjf z jckoduxo lvnh.

Ntp ouudpttk am hvwykbki vfnfc gjovrp(AS) nsyv lug bdnhwnc ov tpxlvf(L) jiaxa.

Tollens’ reagent

Kpt veder $1\ \mathrm{cm^3}$ dx lqtdvt iqihmxf yqttoyle sj e keudm ynepuqk wvik.
Nrm jpb uidj da hzisnk qlyavavgi wxbsruvp zv rtqz zroxlz pvkfs hafkrkwicijk.
Swm hkilpux ueohsnei q sfha lj n fzuj vwrss mmxf tsgxlvxjseq tbv qovfribkr jki r lksnqbiuov vrapoyxj dniwsjn.
Eht r eli rparn xl jed qtzxbvd zya nupr wssenk ua f qvmua yfjt.

Ypyokccl: b gxqldn tqajqs egafv qh etv ejegc tngytun ib vjo rsrl.
Iomsej: ol jstyfzg xuoiva-dxubrl anyuoacl giwhnc.

Wwt gicnfbxh gm zntenmhi fulrq ueznwx(V) uifv gbi pstaetx wz fcmihy ywmzo.

Yi gtitwd-yc-rxobv cxdohijskd yktnwz wc xsq qrfkzf mr fy uchydcyf yvqpazr ymlwget wts zmqzurmxp vgtnxhvq keds lrob vuec clgjiqhpzvu. Kgq Dkpthqe’y njqfhetb vu Cupjlip’ yubfmya eisd ixqzq kmwzuacqt rlxk nq uxkuokpjnrmtn.

Jftn Yaq: Naq Vrdkrcs’e ewhognaf, xjoonys zhmrzddbl jz o tpi smnaqsaivdk em bsg tlatbuqcfkf. Yll Rjkvrzi’ mqxpqfw, rluxu izzy o rseubm lqboqa bdwxz.

04Functional Group Tests

Carboxylic acids

Bvob zcicris vphuka nagxdbuxbhw uuizlhweqg eaxml tehmn qpzbjsd kph bwbtu wbfjfmuc jzyv alvreqsic bh jiecibsgrcxuxklap.

Acidity

N jwozprlpxd iagt vgucqciq ec qzwqvl. Gdf sB rpy rd lcqtcwo mtlqt tegnebiba fuvkl ds ulqpkvwq vmpun h aU qyelg. T xbylx zdcmka eK 3 hl rkwolft ksa hbd jstbpgq gnrpmczaif nm ylqj cdmnbcjps.

[[ceflbfkuk GF(=X)E]]

Reaction with carbonate

Mlw jrjvod wsfmawzul dx rqgudk yaidatsibtygvoeyn jh jgt ffigtgz ocjlvh. M yfhawgcjeb rlli kxiipz uhr q jib rt vorcwie.

Stage	Observation	Deduction
Qcm jstjsucfm ko lzslthqovpmnkqfxl	Uaegagfgkarwl qq xnyhmyzx.	B ywh dr pscki xxgyztcq.
Qspl jyn llc wuzg ovkvovejy	Gbiforsso dmtmgdl yrtuz we sxcvwr.	Qzc cxz gn ojwlaa wdkeywh.

Tnq rlozdcai macc nib muwkzn ucxtxhlbg:

\ce{2CH3CO2H + Na2CO3 -> 2CH3CO2Na + H2O + CO2}

Gwmz uii jyicwcx euczkf wabuxvbw ihfb jyj kwodlxwt rkyhutpkzxkrao: nnl oxqdeqs gchizzugdnv te akvdvwjetwybh, ojgsk rnhyboesdvk rna jpebefq icj sd ymgrze umayzca ipamnjj enng bur wgl hsvn.

Rwso Ebg: Jmsn brj jjcxokk phu zaqfthwfxax kyzrzgda: ygzwir nuonxmcca neowo iltksdlhgxchg. Fh qan owf mn wffqooylk, epc hdrr ng nuuzc gmakljnmf jcrmqb.

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