Lab Report

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Synthesis,*isolation*and* purification*of*benzoic*acid*

Daniel'Southam'(12345678)'

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Daniel Southam

Note the title of this experiment. It does not have to be identical to the procedure outlined in the laboratory manual and should neatly summarise exactly what you achieved.

Daniel Southam

General notes about this exemplar report: This report is for an experiment you have not performed. This experiment is undertaken in Reactivity and Function in Chemistry 120, which some students will undertake. This report, written by an academic staff member, represents a generalised example of the sorts of important information you should include in your report, the common pitfalls that students may encounter, and general information about the style and language expected. Students should read this report in conjunction with the procedure for this experiment, to see how the report differs from the lab manual, how information from the lab manual may be incorporated into the report, and what your demonstrators will be considering when marking your work. IMPORTANT: Your report will be submitted to an automated text matching service that will be comparing your work to a database of previous work by students, literature available publicly, and the internet. Students who are found to submit work that contains significant portions of copied or paraphrased material may be considered to have plagiarised this work and will be reported in accordance with University policy. If you are uncertain or unclear on the definition of plagiarism, or its penalties, see the information on Blackboard. If you want assistance with academic writing you may attend the Learning Centre in Building 303 to gain assistance.

Daniel Southam

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Introduction* The%target%compound%benzoic%acid%(IUPAC%name:%benzenecarboxylic%acid,%see%Figure%

1%(1))%is%a%commonly%encountered%chemical%found%as%an%additive%in%food%(2)%and%wine%(3)%

where%it%inhibits%microbial%growth%at%certain%pHs.%%It%may%also%be%added%to%cosmetics%(4),%

along%with%its%sodium%or%potassium%salt,%to%regulate%pH,%where%its%topical%use%has%been%

deemed%safe%(5).%%The%addition%of%small%quantities%of%compounds%belonging%to%the%same%

family%as%benzoic%acid%illustrates%their%ability%to%alter%the%crystal%growth%of%barium%

sulfate%and%calcium%carbonate%as%barite%and%calcite%respectively%(6).%

Figure'1'Line'structure'of'benzoic'acid'(1)'

Synthesis*

Benzoic%acid%may%be%synthesized%by%addition%of%carbon%dioxide%in%a%Grignard%

reaction%and%subsequent%hydrolysis%to%afford%the%product%(7).%%Alternatively%oxidation%of%

benzyl%alcohol%(IUPAC%name:%phenylmethanol)%directly%or%after%hydrolysis%of%benzyl%

chloride%(IUPAC%name%chlorophenylmethane)%produces%benzaldehyde%which%is%then%

further%oxidized%to%benzoic%acid%(8).%%In%this%synthesis%(see%Figure%2)%oxidation%is%

performed%by%using%potassium%permanganate%and%sodium%hydroxide%under%reflux.%%The%

product%(in%the%ionic%form)%is%then%hydrolysed%by%addition%of%sulfuric%acid.%

Figure'2'Reaction'scheme'for'this'synthesis'(9)'

Daniel Southam

It's important to cross reference within your report to draw the reader's attention to the figures and tables

Daniel Southam

Each separate concept can have different references. In this example one reference talks about the addition of benzoic acid to food, the second talks about wine.

Daniel Southam

The references should be cited frequently throughout the text at any point you've made a statement of fact that you have not created yourself.

Daniel Southam

This paragraph illustrates some important recent research on benzoic acid that illustrates a need for this experiment. It does not necessarily have to directly relate to the experiment undertaken.

Daniel Southam

The captioning tool in Microsoft Word automatically numbers the figures. Note that captions for figures should come below the diagram.

Daniel Southam

ChemDoodle was utilised to create these structures. See the instructions on Blackboard on how to obtain a free copy.

Daniel Southam

Note the use of subheadings to separate out the sections of the introduction. In this case, a discussion on the synthetic technique utilised is appropriate.

Daniel Southam

This reaction scheme has been reproduced from the lab manual, so it should be cited.

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The%crude%product%can%then%be%purified%by%recrystallization%and%the%purity%

determined%by%melting%point.%%The%physical%properties%of%benzoic%acid,%and%the%starting%

material%benzyl%alcohol,%are%given%in%Table%1.%

Table'1'Physical'properties'of'reagent'and'product'(1)'

Property' Benzoic'acid' Benzyl'alcohol' Molecular'formula' C7H6O2% C7H8O% Molecular'weight' 122.122%g%mol–1% 108.138%g%mol–1% Melting'point' 122.35%°C% –15.4%°C% Boiling'point' 249.2%°C% 205.31%°C% Solubility'in'water' Slightly% Soluble%

Aim*

The%purpose%of%this%experiment%was%to%synthesise%benzoic%acid%from%the%basic%

oxidation%of%benzyl%alcohol%followed%by%quenching%the%reaction%with%sulfuric%acid.%%The%

crude%product%was%then%recrystallized%and%purity%determined%by%melting%point.%

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Daniel Southam

General notes about the introduction: This introduction is short, but your introduction need not be much longer. Remember to focus on three important aspects: a) why the experiment might be important, b) what equipment, techniques, or theories are necessary to perform this experiment, and c) what results you might reasonably expect based on previous literature. Your introduction must finish with the aim (or sometimes the research question) that your report will answer.

Daniel Southam

In this experiment the physical properties of reactant and product are very important, and should be included in the report. That's not always the case!

Daniel Southam

Table captions should appear above and summarise its contents.

Daniel Southam

The aim should appear last in the introduction, and need not be exactly the same as provided.

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Experimental* Benzyl%alcohol%(1.04%g,%9.62%mmol)%was%slowly%added%dropwise%to%a%solution%

containing%sodium%hydroxide%(5%mL%of%3%M%solution%in%water)%and%potassium%

permanganate%(2.01%g)%under%reflux.%%A%vigorous%reaction%was%observed%on%each%

addition,%the%next%addition%not%added%until%the%reaction%had%calmed,%and%the%residual%

reactant%rinsed%with%a%small%quantity%of%water%once%completely%added%(ca.%2%mL,%

deionized).%%The%reaction%was%permitted%to%reflux%for%approximately%15%minutes%and%the%

unwanted%byproduct%(manganese%dioxide)%filtered%from%the%solution%containing%the%

product%(sodium%benzoate).%

The%reaction%mixture%was%decoloured%with%a%small%quantity%of%sodium%metabisulfite%

and%acidified%with%sulfuric%acid%until%no%further%precipitation%was%observed%(ca.%5%mL,%3%

M%solution%in%water).%%The%product%was%collected%over%vacuum%and%recrystallized%from%

water.%%A%small%quantity%of%the%crude%product%was%reserved%to%determine%its%melting%

point.%%The%purity%of%the%crude%and%recrystallized%product%was%determined%by%melting%

point%of%a%random%specimen%(Electrothermal%EC1200).%

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Daniel Southam

Each section of your report should appear on a separate page.

Daniel Southam

General notes about the experimental: the important features of the experiment are provided here. It is not necessary to explain to the audience this report is intended for how to achieve a reflux, perform a recrystallisation, or filter by vacuum. This experimental permits any scientist with appropriate training to perform the same experiment (and replicate the same results). The language here is very specific to this type of experiment (synthesis) but the same general principles apply.

Daniel Southam

The use of language here should be strictly third person, past tense, passive voice.

Daniel Southam

See how irrelevant details (setting up glassware, using the apparatus etc) are left out. The reader is intended to be a chemist who can work these details out for themselves.

Daniel Southam

Important observations may also be included, particularly if they may influence the results.

Daniel Southam

The inclusion of masses, volumes, concentrations etc is essential. Sometimes the purity of reagents may also be important to the outcome of the experiment.

Daniel Southam

Timing might be important and should be included.

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Results*and*Discussion* The%initial%synthesis%afforded%a%yield%of%0.9983%g%(85%)%that%when%purified%was%

reduced%to%0.9161%g%(78%),%which%is%within%the%typical%yield%for%this%procedure%(8).%%The%

crude%product%was%noticeably%more%coloured%than%the%purified%product,%indicative%of%its%

relative%purity%and%suggestive%of%the%need%to%recrystallize.%%These%observations%illustrate%

that%the%synthesis%has%proceeded%as%predicted%with%good%yield,%mostly%recovered%on%

purification.%

The%melting%points%(see%Table%2)%illustrated%that%both%the%crude%and%recrystallized%

products%had%melting%points%approximately%that%of%benzoic%acid.%%The%crude%product%was%

found%to%have%a%slightly%lower%melting%point%of%a%wider%range.%%The%lowering%temperature%

of%a%melting%point%coinciding%with%a%broadening%range%is%a%well%known%phenomenon%that%

indicates%the%presence%of%a%solid%solution%containing%significant%impurities%(10).%%By%

comparison%the%recrystallized%product%has%a%melting%point%with%a%narrower%range%that%

strongly%indicates%a%purer%product%as%a%consequence%of%this%process.%

Table'2'Melting'points'

Test' Melting'Point' Crude'Product' 112%–%121%°C%

Recrystallized'Product' 120%–%122%°C%% %

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Daniel Southam

Masses and yields here are results, and should be discussed immediately.

Daniel Southam

General notes about the results and discussion section: this section, for this experiment, is very short due to the nature of the experiment itself. Your R&D may be slightly longer but should include the following important features: a) state a summary of the important findings, b) present data in a meaningful way that permits the reader to compare them visually, i.e. tables, graphs, diagrams, c) Include citations to literature where comparisons are possible, or known theories are important. Things to avoid: including every result, or figure, every finding. For example, if you have more than one calibration curve then showing one in the body of the report as an example is fine, the rest should be included in the appendices at the end of the report.

Daniel Southam

Note the citation, which compares this results to previous results. This illustrates the student clearly was thinking about the meaning of their results and comparing it to others!

Daniel Southam

This discussion is important because it relates to the aims of this experiment.

Daniel Southam

It is appropriate to tabulate these findings, as it permits the reader to easily compare them. Appropriately presenting data is an essential skill.

Daniel Southam

This phenomenon is known, so pointing the reader to somewhere else that explains why is important. Discussing the theory in detail may be irrelevant to the aims of the experiment.

Daniel Southam

This indicates that we have been successful in our experiment and should be stated.

Daniel Southam

Don't forget important information, like units!

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Conclusions*and*further*work* Benzoic%acid%was%successfully%synthesized%by%oxidation%of%benzyl%alcohol%in%good%

yields%comparable%to%literature.%%The%melting%point%indicated%a%product%that%was%impure%

before%recrystallization%that%was%successfully%purified%after%this%processes.%

The%use%of%melting%point%to%identify%the%product%is%limited.%%The%product%may%be%

better%confirmed%as%benzoic%acid%by%utilizing%techniques%that%impart%structural%

information,%such%as%infrared%or%nuclear%magnetic%resonance%spectroscopy.%%This%

synthesis%pathway%may%also%be%compared%with%alternate%pathways,%such%as%the%Grignard%

reaction%between%bromobenzene%and%subsequent%addition%of%CO2%(7),%to%ascertain%which%

provides%a%product%in%better%yield.%

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Daniel Southam

This first sentence answers our aims, without unnecessarily restating the results. It should be short, and to the point.

Daniel Southam

General notes about conclusions and further work: Note this section is concise and direct. The reader should be able to ascertain the major findings and what might happen next. The conclusion should directly answer the aim given in the introduction.

Daniel Southam

Some suggestions for further work mean you know how to improve on this experiment next time.

Daniel Southam

I could use acronyms here, if they were previously defined, i.e. NMR, IR etc. The first time you encounter a phrase that has the potential to be given an acronym, you should define it in full and give the acronym thereafter, e.g. atomic absorption spectrometry (AAS)...

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References* 1.+ Lide+DR,+editor.+CRC+Handbook+of+Chemistry+and+Physics.+85th+ed.+Boca+Raton,+FL:+

Boca+Raton,+FL+:+CRC+Press;+2005.++

2.+ Pastorova+I,+de+Koster+CG,+Boon+JJ.+Analytical+Study+of+Free+and+Ester+Bound+Benzoic+ and+Cinnamic+Acids+of+Gum+Benzoin+Resins+by+GCTMS+and+HPLCTfrit+FABTMS.+ Phytochem.+Anal.+1997+Mar;8(2):63–73.++

3.+ Zoecklein+BW.+Chapter+13:+Sorbic+acid,+benzoic+acid,+and+dimethylcarbonate.+Wine+ analysis+and+production.+New+York+:+Chapman+&+Hall;+1995.+pp.+209–15.++

4.+ Final+Report+on+the+Safety+Assessment+of+Benzyl+Alcohol,+Benzoic+Acid,+and+Sodium+ Benzoate.+Int.+J.+of+Toxicology.+2001+Jan+3;20(4):23–50.++

5.+ Basketter+DA,+Wilhelm+KP.+Studies+on+nonTimmune+immediate+contact+reactions+in+an+ unselected+population.+Contact+Dermatitis.+1996+Oct;35(4):237–40.++

6.+ Freeman+SR,+Jones+F,+Ogden+MI,+Oliviera+A,+Richmond+WR.+Effect+of+Benzoic+Acids+on+ Barite+and+Calcite+Precipitation.+Crystal+Growth+&+Design.+2006+Nov;6(11):2579–87.++

7.+ Pavia+DL,+editor.+Experiment+36B:+Benzoic+acid.+Introduction+to+organic+laboratory+ techniques:+a+small+scale+approach.+Brooks/Cole+Publishing+Company;+2005.++

8.+ Vogel+AI,+Furniss+BS.+Vogel's+Textbook+of+practical+organic+chemistry.+London+:+ Longman+Scientific+&+Technical+;+New+York+:+Wiley;+1989.++

9.+ Southam+DC,+editor.+Experiment+7:+Preparation+of+benzoic+acid.+Reactivity+and+ Function+in+Chemistry+120+Laboratory+Manual.+Curtin+University;+2013.+pp.+7.1–7.10.++

10.+ Blackman+A,+Bottle+S,+Schmid+S,+Mocerino+M,+Wille+U.+10.5+Colligative+properties+of+ solutions.+Chemistry.+Brisbane,+Australia:+John+Wiley+and+Sons;+2012.+pp.+408–20.++

Daniel Southam

General notes about references. You will observe above that no websites are cited (i.e. Wikipedia). However, many of these references were obtained from websites and searches, that include Wikipedia, Google Scholar and the Library Catalogue. Importantly, you should "follow the breadcrumbs" to a verifiable published (and preferably peer-reviewed) source. This includes books and journals. Notice that I've used a mix of both, and have not relied solely on the prescribed text. Note also that these references are consistently formatted using the Vancouver style, with the sequence of numbers reflecting the order of citation in the report. To do this I used Endnote with its built in "Vancouver" style. You could also opt to use the built-in Word citation generator (not particularly good) or manually produce the references list (time consuming).

Daniel Southam

This reference is a good source of physical and chemical properties of many compounds.

Daniel Southam

This reference was cited on Wikipedia and obtained, read and then cited here.

Daniel Southam

This book was available from a search on the Library website for "Benzoic acid"

Daniel Southam

This was cited on Wikipedia.

Daniel Southam

This was cited within reference 4 above, obtained and read before being recited.

Daniel Southam

This is some work done at Curtin by colleagues of mine!

Daniel Southam

This was cited on Wikipedia and available from Google Books to view, which I did before citing it.

Daniel Southam

This is a standard reference for the preparation of many organic compounds. A useful one to know about.

Daniel Southam

This is the lab manual, which should probably be cited at least once if you've used information from it.

Daniel Southam

This is the prescribed text, which was used sparingly!