experiment 8b

Click here to load reader

Post on 22-Oct-2014

734 views

Category:

Documents

6 download

Embed Size (px)

TRANSCRIPT

Experiment 8BQualitative Analysis II

Introduction Qualitative analysis of an unknown organic compound is an indispensible tool in experimental organic chemistry. This method is done in order to determine the possible structures of an unknown sample. The different functional groups present in an organic compound are identified by reacting the sample with different reagents that react that gives a visible result. It is an indispensable tool in experimental organic chemistry as well as other fields such as the study of natural products and biochemistry.

Sodium Metal ResultsSamplen-butyl alcohol Sec-butyl alcohol Tert-butyl alcohol Structure/Formula of compound responsible for visible results H2 H2

Visible Result

Evolution of gas

Evolution of gas

Evolution of gas

H2

Tests for Alcohols

Sodium Metal Type of Reaction: Acid-Base Reaction General Formula:

Tests for Alcohols

Sodium Metal Mechanism

bubbles

sodium alkoxide

Tests for Alcohols

Sodium Metal Complications Dealing with sodium metal can be exciting. Make sure that all samples are dry before proceeding with test.

Tests for Alcohols

Sodium Metal1. What property of alcohol is demonstrated in the reaction with Na metal? What is the formula of the gas liberated? The alcohol exhibits acidic property in the reaction with Na metal. The hydrogen atom is replaced by Na producing H2 shown in the reaction: 2 ROH + 2 Na 2 RO()Na(+) + H2(http://www2.uni-siegen.de/~pci/versuche/english/v44-1-1.html)Tests for Alcohols

Sodium Metal2. Dry test tube should be used in the reaction between the alcohols and Na metal. Why? A dry test tube should be used because Na metal is highly reactive with water and may ignite violently due to the H2 gas produced

(http://www2.uni-siegen.de/~pci/versuche/english/v44-1-1.html)Tests for Alcohols

Lucas Reagent (HCl/ZnCl2) ResultsSample Visible Result

Structure/Formula of compound responsible for visible resultsNone

n-butyl Sec-butyl alcohol Tert-butyl alcohol

No layer Formation of layers Formation of layers

(CH3)2CHCl + H2O(CH3)3CCl + H2OTests for Alcohols

Lucas Reagent (HCl/ZnCl2) Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: Cl General Formula:

Tests for Alcohols

Lucas Reagent (HCl/ZnCl2) Mechanism (SN1 for 2 and 3 ROH)

insoluble layer Tests for Alcohols

Lucas Reagent (HCl/ZnCl2) Mechanism (SN2 for 1 ROH)

insoluble layer

Tests for Alcohols

Lucas Reagent (HCl/ZnCl2) ZnCl2 is a Lewis acid that complexes strongly with the lone-pairs oxygen. This weakens the CO bond and creates a better leaving group.

ZnCl2 also enhances the reactivity of the HCI by polar coordination.

Tests for Alcohols

Lucas Reagent (HCl/ZnCl2) Complications The test applies only to those alcohols soluble in the reagent (monofunctional alcohols lower than hexyl and some polyfunctional alcohols).

Tests for Alcohols

Lucas Reagent (HCl/ZnCl2)3. Why is the Lucas test not used for alcohols containing more than eight carbon atoms? The Lucas test applies only to alcohols soluble in Lucas reagent (monofunctional alcohols with less than 6 carbons and some polyfunctional alcohols). Long chains of carbon makes the compound nonpolar and the OH group less functional. This results to the insolubility of the alcohol in the reagent, rendering the test ineffective.

Tests for Alcohols

Lucas Reagent (HCl/ZnCl2)4. Explain why the order of reactivity of the alcohols toward Lucas reagent is 3>2>1? The reaction of alcohols with Lucas reagent is a nucleophilic substitution reaction. In an S-n1 reaction, the rate determining step is the carbocation. The carbocation is most stable in a tertiary alcohol and is therefore formed faster than a secondary and a primary carbocation. (Solomons and Fryhle)

Tests for Alcohols

Potassium Dichromate ResultsSample Visible ResultStructure/Formula of compound responsible for visible results Cr3+

n-butyl

Blue-green soln

Sec-butyl Tert-butyl

Blue-green Yellow-orange

Cr3+ Cr2O72Tests for Alcohols

Potassium Dichromate Type of Reaction: Reduction-Oxidation General Formula:

Tests for Alcohols

Potassium Dichromate Mechanism

Tests for Alcohols

Potassium Dichromate Mechanism

Tests for Alcohols

Potassium Dichromate Mechanism

elimination

chromate ester

green (due to chromium ion, Cr3+)

Tests for Alcohols

Potassium Dichromate For 1 ROH, RCHO products are further oxidized to form RCOOH

Tests for Alcohols

Potassium Dichromate Tertiary alcohols do not react because there will not be any b-hydrogens to eliminate.

Tests for Alcohols

Potassium Dichromate Complications Aldehydes, which also give a positive test, are better characterized in other ways. The color usually develops in 5 - 15 seconds. Enols may give a positive test. Phenols give a dark colored solution which is not blue-green like a positive test.

Tests for Alcohols

Potassium Dichromate5. Illustrate with equations the reactions of the following alcohols with Potassium Dichromate solution:Proof that dichromate is a strong oxidizing reagent in an acidic soln (0 = 1.33 V) (0 = 0.13 V)

n-butylalcohol

CH3CH2CH2CH2OH + Cr2O7 2CH3CH2CH2COOH

CH3CH2CH2CHO + [O]

sec-butylalcohol CH3CH2CH(OH)CH3 + Cr2O7 2-

CH3CH2COCH3 + H2O

tert-butylalcohol (CH3)3COH + Cr2O7 2- no reactionTests for Alcohols

Ferric Chloride ResultsSample Visible Result Structure/Formula of compound responsible for visible results Fe(OAr)3 Fe(OAr)3 Fe(OAr)3 Fe(OAr)3Tests for Phenols

Phenol Catechol Resorcinol a-naphthol

Brown-black Brownish Brownish green Purple solution

Ferric Chloride Type of Reaction: Complexation General Formula:

Tests for Phenols

Ferric Chloride Mechanism

blue to violet color

Tests for Phenols

Ferric Chloride Complications Not all phenols or enols give positive results. Most oximes, hydroxamic acids, and sulfinic acids give a positive test. Bulky groups on the benzene ring, especially in the ortho position, may cause the experiment to show a negative result. Activating groups attached to the ring decreases the wavelength caused by less electron excitation, thus causing a different color of positive result.Tests for Phenols

Bromine Water MechanismSample Visible Result Structure/Formula of compound responsible for visible results 2,4,6-tribromophenol

Phenol Catechol

Light brown Dark solution

Bromination of benzene ring Tribromoresorcinol2,4-dibromo-1-naphtholTests for Phenols

Resorcinola-naphthol

Yellow with precipitateDark cloudy solution

Bromine Water Type of Reaction: Electrophilic Substitution Substrate: ArOH Attacking Agent: Br+ brown to black solution General Formula:

yellow Br color is removed

Tests for Phenols

Bromine Water Mechanism

Tests for Phenols

Bromine Water The aromatic ring is activated by the hydroxy group, therefore, it can react by electrophilic addition

Tests for Phenols

Bromine Water Complications Mercaptans react readily. HBr is generated, but will not be observed since the reagent is aqueous.

Tests for Phenols

Millons (Hg(NO3)2 in H2O) ResultsSample Visible Result Structure/Formula of compound responsible for visible results Hg complex with phenols Hg complex with phenols

Phenol Catechol

Dark upper layer, light bottomDark solution

Resorcinol a-naphthol

Dark purple Greenish yellow

Hg complex with phenols Hg complex with phenolsTests for Phenols

Millons (Hg(NO3)2 in H2O) Type of Reaction: Electrophilic Addition and Complexation Substrate: Ar-OH and tyrosine Attacking Agent: Hg(NO3)2 General Formula:

Tests for Phenols

Millons (Hg(NO3)2 in H2O) Mechanism1. Nitration of aromatic ring 2. Complexation with mercuric ion

Produces: red complexes and ppt

Tests for Phenols

Millons (Hg(NO3)2 in H2O)6. What functional group is responsible for the observed result in Millons test? Phenol interacts with nitric acid, nitrated phenol reacts with mercury and mercury salts are formed. This reaction accounts for the observed positive result in Millons test.

Tests for Phenols

2,4-dinitrophenylhydrazine ResultsSample Formaladehyde Acetaldehyde Visible Result Yellow ppt Orange, brown(heated) Structure/Formula of compound responsible for visible results 2,4-dinitrophenylhydrazone 2,4-dinitrophenylhydrazone

AcetoneBenzaldehyde

Orange pptOrange ppt

2,4-dinitrophenylhydrazone2,4-dinitrophenylhydrazoneTests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine Type of Reaction: Nucleophilic Addition Substrate: Attacking Agent:

General Formula:

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine Mechanism

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine Mechanism

yellow to red ppt

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine Complications Some ketones give oils which will not solidify. Some allylic alcohols are oxidized by the reagent to aldehydes and give a positive test.

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine7. Why is it disadvantageous to use a strong acid catalyst in the reaction of aldehyde or ketone with 2,4-DNPH? The use of a strong acid reverses the sequence of the reaction. Instead of the nucleophilic attacking the substrate followed by the electrophile, in the presence of a strong acid, the weaker ucleophile attacks the carbon to stabilize the forming hemiacetal. Water abstracts the H+ of the hemiacetal. Hemiacetals are less stable and will form acetals which do not show the visible changes expected of the test.

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine8. Show the mechanism for the reaction of acetaldehyde with the following reagents:a. 2,4 DNPH

Tests for Aldehydes and Ketones

2,4-dinitrophenylhydrazine8. Show the mechanism for the reaction of acetaldehyde with the following reagents:a. 2,4 DNPH

Tests for Aldehydes and Ketones

Bisulfite MechanismSample Visible ResultStructure/Formula of compound responsible for visible results H2CH(OH)SO3- Na+

Formaldehyde

Ppt formation

AcetaldehydeAcetone Benzaldehyde

Ppt formationNo Ppt Ppt formation

H3C(OH) SO3- Na+H3CC(OH)SO3- Na+ (C6H6)CH(OH)SO3- Na+Tests for Aldehydes and Ketones

Bisulfite Type of Reaction: Nucleophilic Addition Substrate: Attacking Agent: General Formula:

Tests for Aldehydes and Ketones

Bisulfite Mechanism

insoluble

Tests for Aldehydes and Ketones

Bisulfite Complications Aryl methyl ketones form the precipitate slowly or not at all. Addition complex stable only in neutral solution.

Tests for Aldehydes and Ketones

Bisulfite8. Show the mechanism for the reaction of acetaldehyde with the following reagents:b. NaHSO3

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO ResultsSample Visible Result

3

solution)

Structure/Formula of compound responsible for visible results

Formaldehyde Acetaldehyde Acetone Benzaldehyde

Purple Red-purple No change purpleTests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO

3

solution)

Type of Reaction: Nucleophilic Addition and Elimination Substrate:

Attacking Agent: Schiffs Reagent General Formula:

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO Schiffs Reagent (fuchsia/pink)

3

solution)

(bis-N-sulfinic acid of p-rosaline hydrochloride) aka fuchsin-aldehyde reagent or Leucosulfonic acid

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO Mechanism

3

solution)

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO Product: Quinoid Dye (purple/magenta)

3

solution)

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO Complications

3

solution)

In this test the reagent should not be heated, and the solution tested should not be alkaline. When the test is used on an unknown, a simultaneous test on a known aldehyde and a known ketone should be performed for comparison.

Tests for Aldehydes and Ketones

Schiffs Test (Fuschine in NaHSO

3

solution)

9. Why is the Schiffs test considered a general test for aldehydes? Differentiation of aldehydes from ketones becomes the main purpose of using Schiffs test since it cannot distinguish one kind of aldehyde from another.

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH) ResultsSample Visible Result Structure/Formula of compound responsible for visible results Ag Ag None

Formaladehyde Acetaldehyde Acetone

Silver mirror Silver mirror Clear

Benzaldehyde

Silver mirror

Ag

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH) Type of Reaction: Reduction-Oxidation Reducing Agent: Oxidizing Agent: Ag(NH3)2+ General Formula:

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH) Mechanism

silver mirror

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH) Complications The test tube must be clean and free of oil if a silver mirror is to be observed. Easily oxidized compounds give a positive test. For example: aromatic amine, some phenols, a-alkoxy and a-dialkylaminoketones.

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH)10.What test will you use to differentiate each of the following pairs? Give also the visible result. Acetaldehyde and acetone Schiffs reagent: acetaldehyde purple solution; acetone no reaction Tollens test: acetaldehyde silver mirror; acetone no reaction

Tests for Aldehydes and Ketones

Tollens Test (Ag(NH3)2OH)10.What test will you use to differentiate each of the following pairs? Give also the visible result. Acetaldehyde and bezaldehyde Acetaldehyde and benzaldehyde can be distinguished from each other using the Bisulfite test since it is also an indication whether the sample is an aliphatic aldehyde or an aromatic aldehyde. Aldehyde will react faster than benzaldehyde because an aromatic ring makes the compound more electron-rich, making the compound less susceptible to nucleophilic attack. Both will form a red precipitate due to cuprous oxide.Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) ResultsSample Visible ResultStructure/Formula of compound responsible for visible results None

Formaladehyde

None

AcetaldehydeAcetone Benzaldehyde

Yellow PptYellow Ppt None

CHI3CHI3 NoneTests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) Type of Reaction: Nucleophilic Addition + Substitutionaddition substitution

Substrate:

I+

Attacking Agent: General Formula:

OH-

Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) Mechanism: Secondary alcohols/ethanol with an adjacent methyl group are oxidized to methyl ketones/ethanal by iodine bleach.

Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) Mechanism (Nucleophilic Addition Part)

Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) Mechanism (Nucleophilic Substitution Part)

yellow ppt

Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI) Complications Test will not be positive if the R group is a diortho substituted aryl group.

Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI)11.What structural feature in a compound is required for a positive iodoform test? Will ethanol give a positive iodoform test? Why or why not? Ketones and alcohols with a methyl group directly adjacent to a carbonyl group or a carbon atom bearing a hydroxyl group react with an alkaline solution of iodine to produce a yellow solid, iodoform. Ethanol will give a positive result because it can be oxidized to an aldehyde with a methyl group attached to a carbonyl group.Tests for Aldehydes and Ketones

Iodoform Test (NaOH/I2KI)12.Show the mechanisms for the iodoform using acetaldehyde as the test sample:

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 ResultsSample Visible Result

Structure/Formula of compound responsible for visible resultsCu2O

Formaladehyde

Brick Red Precipitate

AcetaldehydeAcetone

Brick Red PrecipitateNone

Cu2ONo rxn

Benzaldehyde

Brick Red Precipitate

Cu2O

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 Type of Reaction: Reduction-Oxidation Reducing Agent: (reducing sugar) Oxidizing Agent: [Cu(C4H4O6)2]4 General Formula:

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 Fehlings Reagent: Sodium tartrate, NaOH and CuSO4 forming a copper-tartrate complex

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 Mechanism

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 Mechanism

brick red ppt

Tests for Aldehydes and Ketones

Fehlings Test [Cu(C4H4O6)2]4 Complications None.

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) ResultsTest Samples Visible Result Structure Formula of Compound Responsible for the Visible Result

Glucose1% Sucrose Maltose

Violet RingViolet Ring Violet Ring

1% Boiled Starch

Violet RingTests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Type of Reaction: Nucleophilic Substitution Substrate: furfural or hydroxymethylfurfural Attacking Agent: a-naphthol General Formula:

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Mechanism Dehydration of Hexose Sugar by H2SO4 (elimination)

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Mechanism Dehydration of Pentose Sugar by H2SO4 (elimination)

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Mechanism

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Mechanism

Tests for Aldehydes and Ketones

Molisch (a-naphthol in ethanol) Mechanism

violet

Tests for Aldehydes and Ketones

Benedicts Test [Cu3(citrate)2] ResultsSample Visible Result Structure/Formula of compound responsible for visible results Cu2O Cu2O Cu2O No rxnTests for Aldehydes and Ketones

Glucose Maltose

Brick Red Precipitate Brick Red Precipitate

Sucrose

Brick Red Precipitate

Boiled starch

No change

Benedicts Test [Cu3(citrate)2] Type of Reaction: Reduction-Oxidation Reducing Agent: (reducing sugar) Oxidizing Agent: Cu3(citrate)2 General Formula:

Tests for Aldehydes and Ketones

Benedicts Test [Cu3(citrate)2] Benedicts Reagent: Sodium citrate, CuSO4 and NaHCO3 forming copper-citrate

Tests for Aldehydes and Ketones

Benedicts Test [Cu3(citrate)2] Mechanism

Tests for Aldehydes and Ketones

Benedicts Test [Cu3(citrate)2] Mechanism

brick red ppt

Tests for Aldehydes and Ketones

Benedicts Test [Cu3(citrate)2] Complications Not general for simple aldehydes and ketones. Hydrazine derivatives give a positive test.

Tests for Aldehydes and Ketones

Hinsberg (benzenesulfonyl chloride) ResultsSample Visible Result

Structure/Formula of compound responsible for visible resultsC6H5SO2NRH C6H5SO2NR2 R3NHCl C6H5SO2NRH C6H5SO2NRHTests for Amines

Methylamine Dimethylamine Trimethylamine Aniline n-methylamine

ppt in acid ppt in base/acid ppt in base ppt in baseacid ppt in acid

Hinsberg (benzenesulfonyl chloride) Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: General Formula:

Tests for Amines

Hinsberg (benzenesulfonyl chloride) Mechanism (1 amines)

water soluble

water insoluble

Tests for Amines

Hinsberg (benzenesulfonyl chloride) Mechanism (2 amines)

water insoluble

Tests for Amines

Hinsberg (benzenesulfonyl chloride) Mechanism (3 amines)

water insoluble

Tests for Amines

Hinsberg (benzenesulfonyl chloride) Mechanism (3 amines)

water solubleTests for Amines

Hinsberg (benzenesulfonyl chloride) Complications Amphoteric compounds give erroneous results. Some sodium salts of benzenesulfonamides of primary amines are insoluble in the Hinsberg solution and may appear to be secondary amines. Some tertiary amine hydrochloride salts are insoluble in dilute HCl and water and may also appear to be secondary amines.

Tests for Amines

Esterification ResultsSample Visible ResultStructure/Formula of compound responsible for visible results methyl 2hydroxybenzoate

Salicylic acid

Colorless with wintergreen odor

Tests for Carboxylic Acid + Derivatives

Esterification Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: General Formula:

Tests for Carboxylic Acid + Derivatives

Esterification Mechanism

ester with odor

Tests for Carboxylic Acid + Derivatives

Esterification Complications None.

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Benzamide ResultsSample Visible Result

Structure/Formula of compound responsible for visible resultsammonia

Benzamide

Red to blue litmus Pungent odor

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Benzamide Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: OH General Formula:

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Benzamide Mechanism

basic and pungent

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Benzamide Complications none

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Ester ResultsStructure/Formula of compound responsible for visible results

Sample

Visible Result

Ethylacetate

Loss of Sweet Odor

Acetic acid and Ethanol

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Ester Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: General Formula:

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Ester Mechanism

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Ester Complications none

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Anhydride ResultsSample Visible ResultStructure/Formula of compound responsible for visible results

Acetic anhydride

Acidic

Acetic acid

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Anhydride Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: HOH General Formula:

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Anhydride Mechanism

Tests for Carboxylic Acid + Derivatives

Hydrolysis of Anhydride Complications Higher aliphatic anhydrides and aromatic anhydrides are not readily hydrolyzed with water and thus may not give a positive test.

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) ResultsSample Visible Result Burgundy or magenta color Red to violet color Structure/Formula of compound responsible for visible results

EthylacetateBenzamide

Hydroxamate complexesHydroxamate complexes

Acetic anhydride

Burgundy or magenta colorBurgundy or magenta color

Hydroxamate complexes

Benzoylchloride

Hydroxamate complexes

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Type of Reaction: Nucleophilic Substitution Substrate: Attacking Agent: General Formula:

hydroxamic acid

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Formation of Hydroxylamine

KOH is added to consume the HCl, so that the reaction will not proceed backwardTests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Mechanism for Anhydrides

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Mechanism for Acyl Halides

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Mechanism for Esters

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Mechanism for Amides

Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Ferric Hydroxamate Complex Formation

red/violet/burgundy/magenta color

The solution is acidified by HCl to prevent the excess base from reacting with FeCl3 (a Lewis Acid)Tests for Carboxylic Acid + Derivatives

Hydroxamic Acid Test(hydroxylamine hydrochloride) Complications Some acids will give a positive test. Primary and secondary nitro compounds, imides, some amides, most nitriles, and aldehydes (with no ahydrogens give a positive test. Some sterically hindered amides fail to react.

Tests for Carboxylic Acid + Derivatives

Last Guide Question!13. A colorless liquid has a bp 199-201C and burns with a smoky flame. The sodium fusion test proved negative for the presence of halogens, nitrogen and sulfur. It was not soluble in water, 5% aqueous sodium hydroxide, or 5% hydrochloric acid. However, it dissolved in sulfuric acid with evolution of heat. It did not give a precipitate with 2,4-DNPH solution and did not decolorize bromine-methylene chloride solution. The unknown liquid did give a positive hydroxamate test and was found to have a saponification equivalent of 136. Identify the unknown liquid. Smoky flame indicates that the compound is aromatic. It tested negative for 2,4-DNPH, telling us that it is neither an aldehyde nor a ketone. Negative tests for bromine in methylene chloride solution also indicates that it is neither an alcohol nor a phenol. A positive test for hydroxamate test tells us that it is an acid derivative, which can undergo saponificationtherefore it is an ester. Finally, an aromatic ester with a boiling point range of 199201oC is methyl benzoate.

References http://chemed.chem.purdue.edu/genchem/topicreview/bp /ch9/active.php http://www.biologie.uni-hamburg.de/bonline/library/newton/Chy251_253/Lectures/Oxidation_of _Alcohols/Oxidation.html http://homepages.ius.edu/DSPURLOc/c122/ket.htm http://www.curvedarrowpress.com/partd/tollens.html http://web.pdx.edu/~wamserc/C335W99/Fans.htm http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/ amine1.htm http://www.demochem.de/p30_Z_mol-e.htm

References Hornback, J.M. (2006). Organic Chemistry. 2nd Ed. Belmont, CA: Thomas Brooks/Cole. Shriner, R.L. (2004). Systematic Identification of Organic Compounds. NJ: John Wiley and Sons Inc. Vogel, A.I. (1989). Vogels Textbook of Practical Organic Chemistry 5th Ed. UK: Longman Group.