identify unknown week 4 lecture derivatization experiment

sodium salt of unknown aromatic carboxylic acid + soluble impurities + insoluble impurities total mass: ? g

dissolve in water, filter

insoluble impurities mass: ? g

aq. sol’n of unk. sodium salt + sol. impurities

decolorize, filter

colored dye(s) mass: ~ 20 mg


conc. HCl; filter

crude unk. carboxylic acid mass: ? g

water-soluble imp. recrystallize “pure” unk.

carboxylic acid mass: ? g

melting point (“mp”)

mp, MW, pKa, derivative mp

Identify unknown carboxylic acid

account for all masses; calculate %recovery

CH361/361HWeek4Lecture

DerivatizationExperimentReportWriting

Synthesisofaderivativetoaididentificationofunknownaromaticcarboxylicacid

OH

O

NO2

OH

O

Br

mpt

146 °C

148 °C

mol. wt.

167.12

201.02

pK

2.22

2.85

a 'amide'mpt

176 °C

155 °C

'anilide'mpt

155 °C

141 °C

RNH2

O

'amide'a 1° amide

RNH

O

'anilide'a 2° amide of aniline

H2N

aniline(aminobenzene)

NH3

ammonia

Syntheticschemesforpreparingamidederivatives

ROH

OSOCl2

aromaticcarboxylic acid

N O

dimethylformamide

thionyl chloride

RCl

O

acid chloride(acyl halide)

RNH

O

anilide (a 2° amide)

NH2

CH2Cl2

NH3+ Cl–+

anilinium choride

c. NH3 (H2O)

aniline

RNH2

O 1° amide

+ NH4+ Cl–

ammonium chloride

dichloromethane

aqueous ammonia(ammonium hydroxide)

•extractionwork-up

•filtration/washingwork-up

Reaction Setup

• Dry all glassware in the oven for 30-60 minutes

• Prepare drying tube with cotton & drying agent (CaCl2)

– Prevents moisture from entering the reaction vessel

– Water will hydrolyze the acid chloride

• Heat reaction to 50-60oC via water bath

• Formation of HCl & SO2 (bubbling)

• Transfer to amine nucleophile– Ammonia is gaseous

Image: http://what-when-how.com/organic-chemistry-laboratory-survival-manual/reflux-laboratory-manual/

Open end

Drying tube

CaCl2 (drying agent)

Cotton

Cotton

Inlet adaptor

Condenser

Keck clip & Clamp

Refluxing solvent

Clamp

Round bottomflask

Solvent & reactants

Heat source

Reaction Setup









Open end

Drying tube


Cotton

Cotton

Inlet adaptor

Condenser

Keck clip & Clamp

Refluxing solvent

Clamp

Round bottomflask

Solvent & reactants

Heat source

Reaction Setup









Open end

Drying tube


Cotton

Cotton

Inlet adaptor

Condenser

Keck clip & Clamp

Refluxing solvent

Clamp

Round bottomflask

Solvent & reactants

Heat source

Syntheticschemesforpreparingamidederivatives

ROH

OSOCl2

aromaticcarboxylic acid

N O

dimethylformamide

thionyl chloride

RCl

O

acid chloride(acyl halide)

RNH

O

anilide (a 2° amide)

NH2

CH2Cl2

NH3+ Cl–+

anilinium choride

c. NH3 (H2O)

aniline

RNH2

O 1° amide

+ NH4+ Cl–

ammonium chloride

dichloromethane

aqueous ammonia(ammonium hydroxide)

•extractionwork-up

•filtration/washingwork-up

Useofaseparatoryfunnelforliquid-liquidextraction(phasepartitioning)

RNH

O

ROH

O

NH3+ Cl–

anilinium choride

+ +

anilide

RCl

OH2O

carboxylic acid acid chloride

•likelycomponentspresentfollowinganilideformation

Useofaseparatoryfunnelforliquid-liquidextraction(phasepartitioning)

Extraction via Separatory Funnel

Images: http://www.eplantscience.com/index/dean/liquidliquid_extraction.php

*Make sure to close the stopcock before adding in solvent

**Always hold the separatory funnel at the neck and stoppered end when shaking

***Periodically invert & open the stopcock to release the built up pressure

RNH

O

ROH

O

NH3+ Cl–

anilinium choride

+ +

anilide

RCl

OH2O

carboxylic acid acid chloride

•likelycomponentspresentfollowinganilideformation

Useofdessicantpowdertodrysolutionofamideproductinorganicsolvent(CH2Cl2)

Drying Agent

Dry dissolved derivative over anhydrous magnesium sulfate.– The drying agent is hydroscopic and readily absorbs water.– MgSO4 is ionic and will not dissolve in organic solvent.– Clumps = organic solvent is “wet” (add more drying agent)– Fine powder = solvent is dry (snow globe)

*Make sure to swirl the flask well.

Images: http://quiz2.chem.arizona.edu/vip/extraction/

Percent Yield %yield= )*+,)-./0-1+20340+/*)-./0-1 x100%

Compound Boiling Point (oC)

Molecular Weight(g/mol)

Density(g/mL)

Mass(g)

Volume(ml) mmol equivalence

Carboxylicacid - 156.57 - 0.5071 - 3.239 1.000

SOCl2 166.3 118.97 1.638 - 3.55 5.73 1.77

Aniline 184.1 93.13 1.0217 - 2.05 22.5 6.95

Anilide - 231.68 - 0.5413 - 2.336 0.7212

=weighed out=calculated

Calculationofpercentyield

79

%yield =actual yield (# mols pure substance obtained)

theoretical yield (# mols expected)x 100

%yield =2.336 mmol

3.239 mmolx 100 = 72.12%

48.885.815 15.09

0.5413

2.094 22.49 6.944

sodium salt of unknown aromatic carboxylic acid + soluble impurities + insoluble impurities total mass: ? g

dissolve in water, filter

insoluble impurities mass: ? g


decolorize, filter

colored dye(s) mass: ~ 20 mg


conc. HCl; filter

crude unk. carboxylic acid mass: ? g

water-soluble imp. recrystallize “pure” unk.

carboxylic acid mass: ? g

melting point (“mp”)

mp, MW, pKa, derivative mp

Identify unknown carboxylic acid

account for all masses; calculate %recovery

CH361/361HWeek4Lecture

DerivatizationExperimentReportWriting

REPORT1DUEWED.Oct.31@NOON

Report Writing Philosophy

● Why is writing a report important?

● How does one become a good writer?

• CH 361 Lab Manual • “Report 1 Guidelines” – posted to course website • “Writing Guide” – posted to course website • ACS Style Guide – available to download (see link on course website) • Example of published paper – posted to course website • OSU Writing Center • CH 361 Instructors

● What resources are available to help you write lab reports?

• Communicating results is just as important as obtaining the results! • Learn the professional standards of technical writing in chemistry • “Writing is thinking on paper” (William Zissner) • Improve skills in Word, Excel, ChemDraw and other programs

• Read a lot; write a lot; receive a lot of critical feedback

Typical “Pieces” of a Scientific Report

● Title

● Abstract

● Introduction

● Experimental (“Materials & Methods”)

● Results

● Discussion

● References

● Appendices (not always necessary or appropriate)

Sometimes the Expt’l section appears at the end

Typical “Pieces” of a Scientific Report

● Title

● Abstract

● Introduction

● Experimental (“Materials & Methods”)

● Results

● Discussion

● References

● Appendices (not always necessary or appropriate)

Sometimes these sections are combined

CH 361 Report 1: Guidelines & General Advice

● Abstract section

All major results, i.e., data, should be reported.

● Introduction section

In addition to brief overview of the work reported, give some rationale and/or context for the work being done. Ex., what is its purpose? why was it performed? what are the implications for this work? how does this study fit in with the existing body of work in this field?

● Experimental section

A succinct description of what was done and observed. It should not be written like an instruction manual.

Always include actual amounts, masses, volumes, concentrations, etc; always include observations: color, appearance, etc. Always include instrument information: model number, settings, software, etc.


● Results; Tables and Figures

¾ It’s usually best to include tables and figures in-line with the text, near the first mentioning of the table/figure

¾ Tables and Figures should always be numbered in order of their

mentioning in text, and should always have a descriptive title. ¾ Graph axes should be labeled

● Discussion section

¾ A thorough explanation of what the data means. Describe/discuss the chemistry involved. Provide some error analysis (where pertinent). Draw conclusions based on the data that were collected.

¾ Draw/write chemical equations if reactions were performed (these can sometimes be included in earlier sections, if appropriate)


● Reports need not be written in the order they are read!

● Similarly, one need not present experimental data in the order it was obtained

● References

¾ Use the ACS Citation Format – see course website for details ¾ References should be numbered according to their first mention

in text. References section should include numbered list.

¾ If “literature value” is mentioned, a reference must be given

¾ Textbooks and journal articles are ideal references. Use websites sparingly. “Lecture notes” or “lecture material” should never be listed as a reference.

● Writing Style and Tone

¾ Third person; past tense; “active” voice when possible ¾ Concise and direct language is best

¾ Know your audience

● Grammar, spelling, appearance

¾ Use spell-check!

¾ Feedback – from instructor or peer – is highly valuable


● Writing Style and Tone

¾ Third person; past tense; “active” voice when possible ¾ Concise and direct language is best

¾ Know your audience

● Grammar, spelling, appearance

¾ Use spell-check!

¾ Feedback – from instructor or peer – is highly valuable


REPORT1DUEWED.Oct.31@NOON

identify unknown week 4 lecture derivatization experiment

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