Class admin

• Turn in revision exercise #2

• Pick up and fill out TA evaluation forms– Pink = Adrienne– White = Khadine

Oxygen uptake by Co(salen)

• Notes on part 2 of lab:– Bring stopwatch– Depending on yields, may carry out project as a group

Last week: prepared Co(salen)

• Co(salen) can bind oxygen, just like the biological heme molecule

N

O

N

O

Co

Co(salen)

N

HO

N

OH

O

OHNH2H2N

ensal

+ 2

salenH2

Co(II)

easy

hard

versus

Oxygen binding depends on Co environment

• Co(salen) exists with Co in a 4, 5, or 6 coordinate site• Solvated Co(salen) will bind O2 when it is 5 or 6 coordinate

NO

NO

Co

Active structure

N

O

N

OCo

NO

NO

Co

N

O

N

OCo

Inactive structure

NO

NO

Co

2:1 structure

N

O

N

OCo

O

O

Sol

Sol

NO

NO

Co

1:1 structure

O

O

Sol

• In crystals:

• Solvated:

Mercury view

Experimental apparatus

stopper

vac. flask

water

graduatedpipette

tubing

Co(salen)

DMSO in tt

Which way will the water move? How many SF’s to report?

Graphing data

• What is our:

dependent variable

independent variable

• Which one belongs on which axis?

• How do we best extrapolate to infinite time?

Revision exercise #2

• Goal: submit an improved version of your lab 6 (MIMT) report– Take your report to the University Writing Center for feedback in paper and

electronic form [computers available there]– You can skip the “Questions” section in your re-write – please focus on the

report text (Title, Introduction, Data Analysis, Discussion)– Turn in your original and revised lab reports to me, with UWC comments if

they are available– Due date: Class period on April 30th (two weeks from today)

Note: no other lab report is due that week

• Hours for University Writing Center: – Mon-Wed: 10 AM – 10 PM– Thur: 10 AM – 7 PM– Sun: 2 PM – 7 PM

• Web site: http://writingprogram.hfa.umass.edu/writingcenter/writingcenter.asp• Located in the Learning Commons of the WE DuBois Library

Writing exercise

• Experimental assignment

• Communication error– My intent: spend extra time revising the writing

(conciseness, organization, flow, transitions, paragraph divisions, grammar, readability, style)

– Student interpretation:

GRAMMAR

• Grading – positive points– Will reward effort– Will reward accomplishment

Evaluation of writing in course

• How useful were the lectures on writing

Extremely Very Reasonably Somewhat Not at all

• How useful were the TA comments on writing on the lab reports

Extremely Very Reasonably Somewhat Not at all

• How useful were the instructor comments on lab report 5

Extremely Very Reasonably Somewhat Not at all

• How useful were the UWC comments on writing the lab reports

Extremely Very Reasonably Somewhat Not at all

• Comments for improvement on the writing aspects of Chem242

NA exercise

• 25 pts / problem-10 if SF errors

-5 unit errors

• 25 pts for group work (consistency in answers)

• Positive points only. (Divide points by 10, score will be added to lab 8 grade)

Experimental

• Recrystallization– Solvent temperature – entropic arguments– Evaporation – effect on purity?– Solvent choice (high relative solubility for impurities)– Recrystallization should be done relatively slowly

• Anaerobic environment– vacuum– pump / fill cycles

Coordination of metals in inorganic compounds

N N

N N

HO O OHO

Ferrous Heme

Fe 2+

N

O

N

O

Co

Co(salen)

NO

NO

Co

2:1 structure

N

O

N

OCo

O

O

Sol

Sol

NO

NO

Co

1:1 structure

O

O

Sol

Coordination Number

“dentate”