WEBSITE

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ORGANIC CHEMISTRY LAB II CHEM 333

• WEBSITE
• http//www.uccs.edu/laugenst/chem333/index.htm

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SYLLABUS

• Goals
• Typical lab
• Lab notebook
• Lab reports
• Quizzes exams
• Late lab reports
• Missed labs

• Work efficiently
• Academic policies
• Grading
• Resources
• Disabilities
• Clickers

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SCHEDULE

• Links to powerpoint slides and report forms

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LAB NOTEBOOK

• Notebook Preparation
• Before lab
• Title
• Purpose
• Reference to procedure
• Changes to referenced procedure
• Balanced reaction mechanism
• Table of reagents
• relevant physical properties, amounts, hazards
• Calculate limiting reagent
• Flow chart
• For preparative experiments only

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LAB NOTEBOOK

• During Lab
• Record data
• Amounts actually used, times, temperatures,
  results, etc.
• Record all observations
• Expected unexpected, impacts on yield purity

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LAB NOTEBOOK

• After Lab
• Record post-lab results, physical properties, TLC
  data, spectroscopic data, etc.
• Calculate theoretical and yield.
• Calculate error of physical properties.
• Identify unknowns with name and structure.

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LAB REPORT

• Formatted reports
• Link from schedule
• Typed
• Computer drawn structures
• Turn in completed report form, copies of notebook
  pages, TLC plates, spectra, etc.
• Due 1 week after completion of experiment

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Week 1

• Check-in
• Glassware
• Lab safety
• Lab policy
• Scavenger Hunt (Expt. 3.1)

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Reference Books

• Merck Index
• dictionary by name, use index at back
• CRC
• IUPAC, arranged by parent name
• Chemical catalogs, ChemFinder

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Reference Books

• Safety information
• MSDS sheets in lab
• Web sites (http//www.msdssearch.com/DBLinksN.htm)
  
• Abbreviations
• bp 102.418
• d 1.280 20/4
• sol al, eth

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Reference Books

• Use in CHEM 333
• Molecular weights
• Relevant physical properties
• Structures
• Safety information

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Experiment 3.2ID of an Unknown Organic Liquid

• physical properties
• purity
• identify
• boiling point, refractive index
• develop lab technique
• measurement errors

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Boiling Point

• Dynamic Equilibrium liquid lt--gt gas
• Temperature at which Pvap Patm
• Vapor pressure tendency of molecules to escape
  from the surface of the liquid
• Higher the vapor pressure, lower the boiling
  point
• Lower the vapor pressure, the higher the boiling
  point

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Boiling Point
vapor
liquid
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Boiling Point
vapor
liquid
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Boiling Point
vapor
Pvap Patm
liquid
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Boiling Point

• Effect of non-volatile impurities
• non-volatile low vapor pressure
• non-volatile impurities lower vapor pressure and
  raise the boiling point

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Boiling Point

• Temperature at which Pvap Patm
• Effect of atmospheric pressure
• At sea level Patm 760 torr.
• At higher altitudes atmospheric pressure is lower
  (600-615 torr at UCCS).
• Water boils at 100ºC at 760 torr. Will the
  boiling point be lower or higher at UCCS?

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Boiling Point

• Boiling point depends upon pressure.
• Must correct observed data to 760 torr.
• Use a nomograph.
• Determine of degrees needed for correction.
• typically 5-7 degrees at UCCS

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Boiling Point

• Using the nomograph (see Fig. 1D-1 on p. 29)
• Connect a straight line between the observed BP
  on the left most scale and the observed
  atmospheric pressure.
• Read the number of degrees needed for correction
  where the line crosses the DT correction scale.
• Add the DT correction to observed boiling point

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Effect of Structure

• Intermolecular attractions
• stronger the attractions,higher BP
• 1. hydrogen-bonding (O-H, N-H, F-H)
• 2. dipole-dipole attractions
• 3. VanDerWaals (London)
• CH3CH2CH3 CH3CH2OH CH3OCH3

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Effect of Structure

• Higher MW, higher the BP
• decane gt pentane gt ethane
• propanol gt ethanol gt methanol
• Higher the surface area, higher BP
• straight chain gt branched alkane

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Refractive Index

• Light is refracted (bent) when passes from air
  (less dense medium) into liquid (more dense
  medium)

i
n sin i/sin r
air
liquid
r
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Refractive Index

• n gt 1
• Can read scale very accurately
• 4 decimal places
• Temperature dependent
• Correct data to 20ºC.
• n20 nt 0.00045 (t - 20)

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Pre-lab Preparation

• Read
• Technique D Exercise D2
• Technique E Exercise E1
• Experiment 3.2 A B
• Prepare lab notebook
• Title, purpose, procedural reference
• Changes to procedure
• Table of reagents is not required.
• Pre-lab quiz on WebCT

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Pre-lab Preparation

• Changes to procedure
• Part A
• Use a Craig tube and heat block. Do not use the
  alternate procedure.
• Craig tube must be absolutely dry.
• Measure boiling point of water after measuring
  boiling point of unknown.

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In Lab

• Measure boiling points.
• dry Craig tube and thermometer
• boiling chip (why?)
• 1 mL of liquid
• thermometer 0.5 cm from top of liquid
• Heat with heat block until reflux 1-2 cm above
  liquid.
• Record observed bp when temperature is stable.
• Repeat with water.

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In Lab

• Measure refractive index.
• Use of instrument will be demonstrated by your
  lab instructor.

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In/After Lab

• Calculate corrected values for data
• Boiling Point Data Corrections
• Correct for pressure
• Nomograph
• Correct for thermometer
• Based on boiling point of water using same
  apparatus.
• Refractive Index Data Correction
• Correct for temperature

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Boiling Point Corrections Example

• Data
• BPunk 122oC BPH2O 92oC pressure 615 torr
• Determine DT correction for pressure
• From nomograph DT 6oC
• Determine correction for thermometer
• 100oC (92oC 6oC) 2oC
• Determine normal boiling point of unknown
• BP760 122oC 6oC 2oC 130oC

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Refractive Index Corrections Example

• Data
• nobs 1.3874 t 21oC
• Correct nobs to 20oC
• n20 nobs 0.00045 (t - 20)
• n20 1.3874 0.00045 (21 - 20) 1.3878

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In/After Lab

• Unknowns are liquids in Table 3.2-1
• Compare corrected data with table values to
  identify your unknown.
• Calculate error between corrected data and
  table values.

• Include the name and structure of the unknown in
  your notebook

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Data Collection

• Unknown number
• Ambient pressure, temperature
• Observed data
• Corrected data (include calculations)
• Percent errors
• Unknown name and structure