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有机化学代写 organic chemistry代写

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有机化学代写

Post-Lab Assignment

有机化学代写 With regards to the GC-MS spectrum, a pure molecule such as pentanol will yield multiple lines called the molecular ion isotope pattern.

CAREFULLY READ EVERYTHING IN  有机化学代写

THIS COLUMN:

This is the Postlab Assignment for Exp 4. c Do not scan or hand write anything, unless explicitly directed to do so. Hand drawn images or written words or structures will not receive credit.  有机化学代写

Proper drawing of chemical structures (including bond angles, bond length, etc.) will be closely evaluated. All chemical structures must be generated by you, using ChemDraw, or they will not be graded. To be clear, if you copy/pasted from another source, including a peer, it is deemed plagiarism. See the last page of Exp #1 or Exp #2 postlab assignments for more information about ChemDraw. This is normally very expensive software,but it is free to NYU students!

Ambiguous answers will be counted as incorrect, so please provide concise but explicit answers. Clarity,details, and proper use of terminology matter.Explanations for questions are typically valued as much or more than the simple answer. Also, all “non-wrong”  explanations are not considered equal.

Your assignment must be submitted to NYU Brightspace (for authenticity evaluation) under the Assignments tab as a complete electronic file (no hand-writing/drawing),AND as a hard copy to your section instructor.

All sections may submit your hard copy and electronic copy of the assignment by the start of your Exp #5 laboratory session.

Failure to submit both forms of your report/postlab assignment at the start of your lab session will result in a 25% penalty. Failure to submit both forms of your report/postlab assignment within 24 hours of the due date/time will result in a score of zero.   有机化学代写

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All report/postlab assignments must be  completed INDEPENDENTLY. If you fail to  comply with this rule on part of your assignment, then your entire assignment will be scored as a zero. Further, all of your coursework to date will be subjected for thorough review for originality.

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Be sure to put (1) your name, (2) section number, (3) section instructor’s name, and (4) the due date at the top of your postlab assignment. A 2 point deduction will be assessed for each missing item.

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Do NOT include the following questions in the document you submit, ONLY include your answers in the document you submit. A 10 point deduction will be assessed if the text from the postlab document is included in the document that you submit.

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← ←  ← READ this entire column carefully.  有机化学代写

You will probably find at least half of the problems to be rather shorter than they appear.

1) Even though you may have carried out the column chromatography portion of this experiment with a peer,your postlab assignment must be completed independently. To be safe, it is advisable that you not communicate with your co-experimenter regarding thisassignment.

i) What eluent did you use for your TLC analysis?

ii) What are the Rf values for fluorene and 9-fluorenone on your TLC plate? Clearly indicate the value for each. Show calculations.

iii) How would each of the Rf values be different if you used 100% hexanes as the mobile phase?

iv) Is it possible to have an Rf value that is greater than 1? Justify in two sentences or less.

v) Based on your TLC results, was your attempt to achieve pure fluorene and pure 9-fluorenone successful? Justify your conclusions in three sentences or less.

2) You all tested the concentration of your column fractions on a scrap TLC plate, and then adjusted the concentration before spotting each solution on your new TLC plate. Answer the following based on what you should do, not what you did (in case those are different).

i) Imagine that your first test spot directly from the collection flask of Fraction 2 was too light when visualizing using the UV light. Describe what you could do in order to achieve a more appropriate spot on your TLC plate. Justify your answer in two sentences or less.   有机化学代写

ii) Imagine that your first test spot directly from the collection flask of Fraction 3 was too dark when visualizing using the UV light. Describe what you could do in order to achieve a more appropriate spot on your TLC plate. Justify your answer in two sentences or less.

3) If propyl benzoate has a Rf = 0.7 when using a 30:70 ethyl acetate : hexanes as the eluent, then under the same conditions:

i) draw one molecule that would obviously have an Rf greater than 0.7. Justify your answer in one sentence.

ii) draw one molecule that would obviously have an Rf less than 0.7. Justify your answer in one sentence.

Reminder: As always, use ChemDraw to create structures for your assignments. Ambiguous answers are incorrect.

有机化学代写
有机化学代写

3) Let’s reflect on previously learned purification strategies and consider the reaction outcome from Exp #3 (addition reaction).  有机化学代写

We know that the reaction did not go to completion. For this problem assume the following to be true: (1) at the end of the reaction 40% of the starting material was converted to the desired product (2- proplybromo)benzene), (2) there was no minor product or side product formed, (3) our purification methods during the Exp #3 session removed all of the impurities except for the starting material and desired product.  有机化学代写

(i) Why is extraction not a reasonable method to separate the starting material and desired product?Justify your answer in two sentences or less.

(ii) Why is recrystallization not a reasonable method to separate the starting material and desired product? Provide a justification, which must be both significant, and based on either different principles or different chemical properties from the answer to‘Part i’ of this question.

(iii) Column chromatography, using the materials that we used in Exp #4, is a reasonable method of separating the Exp #3 starting material from desired product. Explain why in two sentences or less.

(iv) Even if the desired reaction product, (2-proplybromo)benzene, is isolated using the conditions of Exp #4, it will exist as a racemic mixture (recall the lab lecture, and/or Chapter 4 of the lecture textbook). How could you modify the Exp #4 column chromatography experiment conditions in order to separate the components of the racemic mixture. Justify in three sentences or less.

5) As you learn more about organic molecules and their structure and reactivity, you can imagine separating organic compounds from a mixture.

One place you find lists of mixtures of organic compounds is in packaged  foods (note that organic compounds are found in non-organic food– different meanings of “organic” in each case). Your task is to identify two organic compounds in the same packaged food (not pharmaceutical product) that you could separate from each other using column chromatography. For the purpose of this exercise you may assume that you can ignore all other components of the packaged food. Your answer should include:

(i) The specific brand name and product name of the packaged food

(ii) The two chemical structures with the common name or IUPAC name listed below for the structure two compounds.

(iii) Predict the order of elution from a column if a mixture of these two compounds were to be purified. Justify your answer in two sentences or less.

6) In an attempt to distribute the content, this question requires you to view two 14-15 minute mini-lectures found on the following topics (view in this order):

  • Gas Chromatography with a Flame Ionization Detector  (GC-FID)
  • Gas Chromatography with a Mass Spectrometer  (GC-MS)

The videos may be found on the Lab website, More Tools tab, Media Gallery sub-selection.  有机化学代写

After you view these videos, answer the following questions. This will help to introduce you to content that is needed for your next lab session (Exp #5); basically this is required pre-lab preparation.

(i) With regards to the GC-FID spectrum, what chemical correlates with the retention time?

(ii) With regards to the GC-FID spectrum, what information can be approximated from the area under the curve?

(iii) With regards to the GC-MS spectrum, a pure molecule such as pentanol will yield multiple lines called the molecular ion isotope pattern. At what m/z values would the two most significant/largest lines be observed? Why are there multiple lines?

What does each line represent? Be specific about the identities of the species. Answer in four sentences or less (structure(s) may be included if you wish to assist in the answer).

 

有机化学代写
有机化学代写
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