Chem 31.1 Experiment 8A-E Handout

Experiment # 8A - QUALITATIVE ANALYSIS (A-E) Avila, Kimberly & Pascual, Ian Group 7, Chem 31.1, AB1, Ms. Sarah Sibug May 15, 2014

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ACETYLENE GAS CaC2 + 2H2O ---> C2H2 + Ca(OH)2

ALKYL HALIDES - alcoholic AgNO 3 test • silver nitrate in ethanol was used to separate the RX bond and create AgX • Although pure water is polar and a protic solvent, it cannot initially dissolve the alkyl halides. Therefore ethanol is used because the final product AgCl is insoluble in polar solvents • SN1 since ethanol and -NO3 are both weak nucleophiles • AgCl = white precipitate • AgBr = pale yellow precipitate • AgI = yellow precipitate • stability of the carbocation created by the leaving group dictates reactivity. Stability: tertiary (3 0) > secondary (20) > primary (10). • chlorobenzene should not react since the removal of Cl would make the ring positively charged. Benzyl chloride can because the charge is on the methyl group

AROMATICITY - nitration • Aromatic rings have less reactive π bonds and undergoes electrophilic aromatic substitution • H2SO4 as a catalyst would protonate HNO 3 and make NO2+ and H2O. -NO2 would substitute an H from the ring in the ortho or para position, especially since xylene has two methyl groups, giving 2,6-dimethylnitrobenzene (C8H9NO2)

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However, since benzoic acid has a deactivating COOH attached to it, the -NO2 would attach in the meta position

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+ = weak almond smell and oily yellow solution

indicates the acidity of the H bonded to the carbons in triple bonds AgNO3 / NH4OH

HCCH ----> AgCCAg + 2HNO3

http://www.orgsyn.org/demo.aspx?prep=cv1p0372

ACIDITY/BASICITY - AgNO3 test • carboxylic acid would react with AgNO 3/ethanol to form a carboxylate salt with Ag • + = white precipitate • HNO3 would lead to the H atom attaching to the carboxylate ion, forming the carboxylic acid again and dissolving the precipitate which would not happen if AgX was created instead. • Acetic acid = CH3COO-Ag+ •

Benzoic acid = AgC7H5O2 AgNO3

HNO3

RCOOH ------>RCOO- Ag+ ----->RCOOH ethanol

- Silver acetylide test • Tollen's reagent (ammoniacal solution of silver nitrate) can be used to replace the hydrogen bonded to the sp carbons • releases silver acetylide (AgCCAg) and HNO 3 • useful in differentiating acetylene/ethyne (HCCH) with ethylene/ethene (H2CCH2) UNSATURATION

- Br2/I2 in CH2Cl2/CHCl3 • methylene chloride or chloroform are inert solvents; do not affect • electrophilic addition; no react with aromatic • + = removal of color of Br2/I2 RHC=CHR --------> R(Br)HCCH(Br)R - Baeyer test (KMnO4) • for presence of alkenes and alkynes • Baeyer's reagent is an alkaline solution of cold KMnO4 • + = brown precipitate from MnO2 • E+ addition, react only with styrene and ethyne

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Jones' reagent (K2Cr2O7) oxidizes H attached to carbon where OH is attached. 30 alcohols therefore do not react. + = green color (Cr3+) excess of primary alcohol with lack of oxidizing agent creates aldehydes

excess of oxidizing agent creates carboxylic acid 20 alcohols create ketones

H2O

H2C=CH2 -------> (OH)H2CCH2(OH) + MnO2 H2O

HCCH -----------> (OH)2HCCH(OH)2 + MNO2 - Ignition test • burning of aromatic ring or unsaturated is incomplete combustion • + = yellow flame and soot • soot is the deposited carbon. The more sooty the result, the higher the degree of unsaturation • increase in blue flame indicates increase in O2 • assuming complete reaction: C6H6 + 7.5O2 ----> 6CO2 + 3H2O C6H14 + 9O2 ----> 6CO2 + 6H2O C6H6 + O2 ----> CO2 + H2O + C(s) ALCOHOLS - Na metal • acidity of alcohol determines rate of bubbling because hydrogen released is the acidic H. Therefore, 10 > 20 > 30

PHENOLS - FeCl3 test • + = colored complex (ferric phenoxide) • colored complex may also be due to the solvent used, as some phenols will color in chloroform, alcohol, or aqueous. pyridine

3ArOH + FeCl3 ------>Fe(OAr)3 - Br water test • + = discoloration • OH attached to benzene is very receptive to E +. Therefore bromination occurs

ROH + Na -------> RO-Na+ + H2 - Lucas test • Lucas reagent (ZnCl2 + HCl) converts OH to alkyl chloride. • + = formation of layer • alcohol solubility in reagent is limited to 6 carbons • stability of carbocation created determines rate of layer formation. 30 > 20 > 10 • 10 - RCH2OH + HCl ----> non • 20 - R2CHOH + HCl ----> R2CHCl + H2O • 30 - R3COH + HCl ----> R3CCl + H2O

- Jones test

- Millon's test • + = colored complex (red?) • Millon's reagent ((Hg(NO3))2 in H2O) creates mercuric salts • test for 4-hydroxyphenylalanine • Mercurous and mercuric ions in nitrous and nitric acid