Category Archives: General

Chirality in Drugs

Many drugs are optically active compounds.  Often it is only one enantiomer that has the desired therapeutic effect.  Thalidomide, a drug used to treat morning sickness in pregnant women in the 1960s is an example of this.

The two enantiomers of Thalidomide

The R isomer (pictured on the right above) acts as a sedative while the S isomer (pictured on the left) has teratogenic properties that resulted in thousands of children being born with deformities.

Thalidomide was produced and sold as a racemic mixture of the two enantiomers which resulted in the birth defects.  Even if it was produced in a pure enantiomeric form, this wouldn’t have solved the problem as there is evidence that the enantiomers can convert under physiological conditions.  Mass producing pure enantiomeric forms of drugs can be expensive and low yielding.

Taxol is another drug that has a complex level of chirality.  In total, Taxol has 11 asymmetric carbon atoms.  Taxol is used to treat cancer and is a naturally occurring substance that is found in the bark of Yew trees.

The structure of Taxol

Obtaining Taxol from its natural source is extremely low yielding and causes environmental damage as it destroys the trees.  Synthesising the drug from scratch in the laboratory would require a large multistep process that would also prove low yielding and extremely costly.

As such, a compromise is found and the drug is produced by a semi-synthetic route starting with a material found in the needles of the Yew tree.

This is a more advantageous method as harvesting the needles of the tree does not cause as much environmental damage and significantly lessens the number of steps needed to manufacture the final product.  In addition, the overall yield of Taxol is improved compared to extraction from the bark.

The challenge in the synthesis is creating the correctly oriented chiral centres.  This is done through a method known as asymmetric synthesis.

 

Asymmetric synthesis involves using a chiral auxiliary attached to the molecule to force through steric hindrance the predominance of one enantiomer over another.

Consider the achiral molecule below.  It is possible to make two enantiomers by adding an amino group to carbon 2.

If you want to favour the production of one enantiomer over the other, attaching a chiral auxiliary molecule to force the addition of the amino group by blocking the path of attack from one side of the molecule.  Below is an example of one such chiral auxiliary.

Notice how the addition of the chiral auxiliary hinders attack from one side of the molecule.  This doesn’t eliminate the production of the unwanted enantiomer but greatly decreases it.

Once the reaction is complete, the chiral auxiliary can be removed for reuse and the final product isolated.

Alkenes

Reactivity

Alkenes are more reactive than alkanes.  Electrons in π bonds are not as strongly attracted to the nuclei as the electrons in the σ bond.  This makes the π bond weaker.

✍️    HL – What is the hybridisation of carbon in this molecule?  If you can’t answer that question, you need to revise this section from bonding.

A model of ethene showing the electron distribution

Distinguishing between alkanes and alkenes

✍️   Review this summary of alkenes and add your own summary to your notes.  Include an example of the reaction that occurs when adding bromine water to an alkene.

✍️  What type of reaction is occurring in the alkene test tube?

✍️   If left overnight, the test tube containing the alkane would also decolourise.  Write a set of equations to explain this and identify the type of reaction occurring.

Addition reactions

Alkenes can react with:

  • halogens eg F2, Cl2, Br2 and I2
  • hydrogen halides eg HF, HCl, HBr and HI and
  • water H2O in the presences of a sulfuric acid catalyst
  • hydrogen in the presences of a Ni catalyst

✍️  Write the equation for the reaction of but-2-ene with each of the following reactants above.  Use structural formulae in the equations and name the product each time.

✍️  What classes of compounds can be made from addition reactions of alkenes?

Addition Polymerisation

View the video found on this page.

Review pages 3 and 4 of this summary and write your own notes.  Make sure you view both the animations.

Key terms to remember here are monomer and polymer.  Make sure you can define both and know how one relates to the other!

Try the polymer puzzles found here.

Alkenes are useful compounds.  You can read about them here.

This concludes the material for standard level.  You should now read the section in your text book (10.2) which is relevant to alkenes and addition polymerisation and add any thing else you find important to your notes.

Practice problems   and    solutions

Electrophilic Addition Reactions – HL only

Study the following image of a general mechanism for electrophilic addition reactions.  What do you think it is showing you?  Think about the following:

  • What do you think the curly arrows are representing?
  • What does r.d.s stand for?
  • Why is the second step faster than the first step?

The above diagram is the general mechanism for electrophilic addition of any halogen (X2), halogen halide (HX) or interhalogen (eg I-Cl or iodine monochloride) with any alkene.

✍️  Draw the mechanism for the bromination of ethene.

Remembering that an electrophile is an electron deficient species, how is Br2 considered an electrophile in this mechanism?

Below is the reaction between propene and HBr.

As you can see, there are two possible products.  One is more likely than the other.

✍️  Draw the mechanism to create both the products.

The Markovnikov rule explains why 2-bromopropane is the major product.  Simply put the Markovnikov rule is…

“The hydrogen rich get richer!”

✍️  Use your textbook to read about this rule and write a summary to explain why the major product is 2-bromopropane and not 1-bromopropane in terms of the stability of the carbocation.

Practice problems  and  solutions

The Gas Laws

1.  Avagadro’s Law

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Take a look at one or more of the following sources that explain this law.  Alternatively, read chapter 1.3 in your textbook.

✍  Make your own summary in your notebook.

Avagadro’s Law Sources

✍  Now apply the Law by completing these questions:

Avogadro’s Law questions and their answers.
Find more questions in your textbook.

2. More Gas Laws

You can use the PhET simulation below to see the various changes in temperature, pressure and volume of a fixed amount of gas when you change one of these variables.

Gas Properties

Click to Run

 

A summary of the various gas laws defining the relationships between volume, temperature and pressure are found below.

V = volume in dm3
T = temperature in K
P = pressure in kPa

Note that these relationships are not given to you in the data booklet.

These laws can be represented graphically too.

Read the section in your textbook, and look at the sites mentioned for Avogadro’s Law to find more information if needed.

✍  Write a summary in your notebook.

3. Kinetic Theory of Gases and the Ideal Gas Law

The kinetic theory describes a gas as a large number of submicroscopic particles (atoms or molecules), all of which are in constant rapid motion that has randomness arising from their many collisions with each other and with the walls of the container.

✍  The kinetic theory of gases is used to describe the motion and behaviour of an ideal gas.  Using your text and other relevant sources, describe the differences between an ideal gas and a real gas in your notebook.

The molar volume of any gas at STP (standard temperature and pressure) is represented below.

Screen Shot 2016-09-05 at 1.16.53 PM

Warning!Warning!Warning!Warning!Warning!Warning!Warning!Warning!Warning!
Many sources quote the molar volume of a gas as 22.4 dm3.  This is using a standard pressure of 101.3 kPa NOT 100 kPa which is the new standard adopted by the IB!  Beware of past paper questions using the old value!  The new value has been used only since the 2016 exams!  If in doubt, check your data booklet – the value is quoted there as 22.7 dm3.

Combining all the equations so far, we can derive the ideal gas equation.  This is in your data booklet as is the value for R which is the ideal gas constant.  Check to make sure you know where to find these.

You will need to be able to solve problems based on these laws.  Once you feel comfortable with them and you have read and taken relevant notes from chapter 1.3 in your text, you can try the following problems.

Problems
Answers (remember that some of these might use 22.4 instead of 22.7 as the molar volume of an ideal gas at STP.)

Studying for IB Chemistry

johnny-automatic-look-it-up-300pxIB Chemistry is a challenging subject whether you are doing SL or HL.  Content heavy subjects can be tricky so here is a guide with some practical tips for studying.

How much time should I spend studying?

This is different for different people and you will need to work out the best course of action for you.  The research says though that distributed practice is more effective than mass practice for learning.  In other words, forget cramming!  After first semester of grade 11, the volume of content covered makes cramming too difficult anyway.  And you definitely want to avoid having to re-learn the course every time you sit a test or exam.  Better to learn it as you go!

So what does this mean?  Here are some guidelines.

    • Students who are feeling less confident
      30 minutes of study every other day or 4 days a week
  • Students who are feeling more confident
    30 minutes of study 3 times a week

These are guidelines which you need to adjust for your own needs.

When should I study?

You need a routine and you need to stick to it.  IB students have an incredibly packed timetable.

  1. Map out your schedule.
    Use a calendar app like Google Calendar or iCal to map out your schedule.
    Put everything on to it and see where the gaps are.

Include in your calendar:

  • Your class schedule (easy to subscribe to from Veracross)
  • Your clubs and after school commitments like sports etc
  • Time to do homework – this is separate from studying!
  • Free time – time to play, exercise, watch tv or whatever!
    1. Note where the gaps are and allocate those times for study for various subjects.
      If you see that there isn’t enough time, you may need to make some adjustments and prioritise.  Are you over committed with clubs/sports?  Free time is important for balance but 3 hours a night is just as unbalanced as no or little free time!
  1. Display your schedule.
    Print this out and put this up somewhere near where you study.  Share it with your parents so they can help support you too.

How should I study?

In Chemistry there are basically three things you need to do:

  1. memorise information
  2. understand chemical concepts deeply enough to apply them
  3. perform certain skills eg calculations

You need to study differently for these three different tasks.  Here’s how.

Memorising Information

There are lots of definitions, formulae and diagrams that you need to be able to recall.  Often these are one point questions on the exam but all those one pointers add up!  Don’t miss out on easy marks!

Here are two strategies for memorising information.

    1. Flashcards
      Whether you use a program like quizlet or if you just make them by hand, practicing with these for a few minutes regularly will quickly find you memorising things fast.  If you use quizlet it is important that you complete the learn function before trying any of the games or tests.
  1. Hand writing
    Many people find writing information out by hand again and again until you can do it from memory to be more effective for memorising.  Have a master copy of everything you need to memorise (like your definitions sheet).

Below is one page of Rino’s definition doc.  Notice how she has organised the information in a way that works for her – by topic.  She has also included diagrams and other information she feels important to remember.  Creating this document also makes her think about what information is important to include.  She can then use either of the strategies above to memorise the information.  And she can ask her parents or friends to test her knowledge from the sheet.

Understanding chemical concepts deeply enough to apply them

This is trickier.  Many students think that just re-reading their notes or text is enough but this actually doesn’t help much.  Here are some strategies you can use.

    1. Reading before and after class
      Read the section in your text that we will be covering in class before the class.  Then when you get home, re-read the same section.  This doesn’t take very long and you can do it on the train!  You’ll be surprised how much you will remember the following class if you do this!
        1. Close your textbook/notes and make a map!
          Without consulting your notes or textbook, organise what you know on a piece of paper from memory.  Use a pencil so you can add, change and delete as necessary.There is a lot of ways to organise your information.  Here are a few possibilities:

          Organise with headings
          Organise using appropriate BrainFrames™ (use multiple types depending on the information) or other types of concept maps you’re familiar with.Give examples where possible
          Use colour to group related ideas
          Use arrows or lines to connect related ideas or
          Group related ideas by position on the page


          Now open your notes or text and add anything you missed or didn’t include correctly.  In you next study session, repeat the exercise until you can produce a map/summary with all the information you deem important from memory.Keep and display your best one.  Add to it when concepts from other topics connect to it.  This should be growing and changing as you move through the course.

                  1. Keep a list of questions / confusing points
                    Write down any questions you have from reviewing past material and answer them as soon as possible.  Here are a list of resources you can use that might have the answer immediately:

                    skype a peer
                    your text book
                    try a tutorial video from Dr Richard Thornley or Mike Sugiyama Jones
                    IB Chem wikibooks
                    Chemguide
                    IB Chemistry Web
                    InThinking IB Chem website for students


                    No joy?
                    Here are some things you can do to get help that isn’t immediate:

                    email your teacher
                    post your question to IB Chemistry @ YIS
                    post your question to a student forum like IB Survival
              1. Form a study group
                Discussing concepts with your peers is a great way to solidify your understanding.  Use a study hall at school, an arranged meeting time in the library or arrange a skype chat.Here are some tips on making this effective:

                Make it a once a week deal.
                Be prepared – agree on what you will discuss before the meeting so you can review a bit before hand and identify the tricky bits you need help on.
                Talk – don’t just sit back and listen.  Actively participate.  Ask questions.
                Decide on the next meeting and topic before the end of the current meeting.

                Below is a protocol you can follow in your study group.   Just make a copy!

Practicing skills

Often this involves calculation practise.  Like everything else you should spread this out.  Don’t practice ∆H calculations from Bond Enthalpies for 3 hours and then never do another problem for six months!  Once you feel confident with a type of calculation, do one problem of that type every couple of weeks or so to keep it fresh.

If there is a certain type of calculation you find hard, start with easy examples and work up.  And if the easy ones stump you – seek help immediately!

Where can you find problems to practice?

  • Your text book – do them all!
  • The problem sets posted on IB Chemistry @ YIS
  • Search for them on the internet
  • Ask your teacher

Finally, you will need to practice exam type questions.  You can do this by re-doing old tests, practicing past paper questions supplied to you by your teacher or that you find on the internet.  You should do these under timed conditions (roughly 1.5 minutes per mark) so you get used to the pressure.

How to get motivated

This is the big one!  Lots of people know what they need to do but getting motivated to sit down and do it is really hard.  I struggle with this all the time.  Here is what works for me most of the time…

Finding the right time

I schedule everything.  I know that I work best in the mornings, so I try and do some work before school starts – this is easy for me because I don’t have a long commute.  I also look at my schedule for the next day and plan before I finish for the evening, what I’m going to get done the next day and when.  This helps a lot.

Finding the right place

Make sure you have the right environment that is conducive for your study.  Make sure your desk or work space is clear and you have everything you need.  Don’t respond to emails, texts, skype etc whilst you are working.  Put your phone on silent.  Leave these distractions for when you are on a break as a reward.  Listen to quiet instrumental music.

Small chunks is key

I use something called the Pomodoro technique.  This involves breaking down my work/study into 25 minute chunks.  Knowing I only have 25 minutes of work before I get a break makes it easier to start.  I decide how many 25 minute chunks I’m going to do, and then I count them down.  My record is 16!

 

Let’s share our best tips!

Do you have a technique that works really well for you?  Please share it by commenting on this post.  I want to keep adding and refining ideas and techniques to this post to make it the best resource possible!

 

Image credits

Look it up! by Johnny Automatic and shared on OpenClipart.org

Grade 11 A and B – Cover work for Friday

Google hangoutHi Grade 11’s.  I’m sick and at home.  I will be online during your class today though.  If you need my help, or want to ask me something, you can google hangout me from our Google+ community!

Just click the hangout button on the top right corner and search for me.

Here is the work you need to do today….

Homework check

Check your homework.  Hopefully you marked your homework already since it is out of the text book.  If there were any questions you got stuck on, discuss them at your table.

If you still can’t solve the problem, post the question on the Google+ community (atomic structure category) and I or someone else in the community will get back to you!

The Electromagnetic Spectrum

Take a look at the following graphic.

Take a few minutes to study this graphic yourself.  With a partner, discuss the following:

  1. What do you see?  Describe the picture.  Point out all the features shown on the graphic.
  2. What do you think?  What is this graphic about?  What is it trying to show you?  How might this be related to our topic on atomic structure?
  3. What do you wonder?  What questions do you have about this graphic?  Is there anything that confuses or puzzles you?

It is important to note how frequencyenergy, wavelength and colour change across the spectrum.  Make sure you’ve noted what increases and what decreases as you move from left to right.

The Hydrogen Spectrum

Use headphones to watch the media on this post together with your partner.  If you are lucky, Mrs Harrison may be there to show you the hydrogen spectrum on our special carousel!  If not, I will show you next week.

Draw and label a diagram showing all the possible transitions by electrons to the first, second and third energy levels.  Include the following on your diagram:

  • Name the series
  • What type of electromagnetic radiation is emitted when the electrons drop to the lower energy level (ie UV, visible light or infrared).
  • Label the energy levels on the y-axis

Watch the following video that talks about where electrons hang out around an atom.

Discuss with your partner what this video is talking about. Draw the shapes of an s orbital and the three p orbitals in your notebook.

Conclusion

Take a moment to add any new information that is relevant to one or more of your questions on your fish diagram.  If you have some questions from the material presented today, put them on the Google+ in the Atomic Structure category.

If you have time left, you can use it to work on your lab report.

Introductory Activities for Plants and the Biosphere

Hello Grade 7!  Here is some background work to do for our new topic.  Some of this will be familiar from grade 6.

Plants have a vital relationship with every other type of organism on Earth, because of their special ability to transform energy from the sun into chemical energy.

  1. Watch the brainpop videos on:
  • Food chains
  • Photosynthesis
  1. Complete the workbook given to you as a handout.  (There will be a stack of them on my desk).
  2. Take the quizzes for both videos and send the results to me.  You need to get at least 8/10 for both quizzes before going on to the next step!
  3. Finish writing your conclusion and evaluation for your science fair project and complete your Science Fair Planner.
  4. Only after all that is done, can you play the Food Fight game on BrainPop!

 

Grade 7A and 7B – Cover work for February 9 and 11

Hello Grade 7!

Here is what you need to complete during Monday’s double period.

  1. Log in to BrainPop using the nine dots!
  2. Watch the BrainPop Video on the “Digestive System”
    Screen Shot 2015-02-04 at 7.28.53 PM
  3. Take the quiz and submit results to me on a spreadsheet!  You need to get at least 8/10 before going to the next activity.
  4. After you have become an expert on the digestive system, choose the “Make-a-map” option.
    Screen Shot 2015 02 04 at 6.19.36 PM
  5. Arrange the images in the correct order and label them to make a map of how the digestive system works.You do not need to include every image and every keyword in your diagram.  Just use the ones that make sense to you.Here is an example of the concept map I began.  You could start yours like mine or choose to do it totally differently.
    Screen Shot 2015-02-04 at 6.29.32 PM
  6. Save your finished map and submit to teacher.
  7. Finished?  Need more?  Watch the movie below.
  8. Read pg 8 of Spotlight Science 8.
  9. In your notebook, put the heading Digestion.
  10. Answer question 1 in your notebook.

 

7A(nimals)  –  Here is what you need to complete on Wednesday’s double period.

  1. Log on to BrainPop using the nine dots.
  2. Watch the video “Nutrition”
    Screen Shot 2015-02-04 at 7.26.40 PM
  3. Take the quiz and send the results to me via a spreadsheet.  You need to get at least 8/10 before you proceed to the next step.
  4. Investigate a diet.

    Many people choose different diets for different reasons.  For example, some people are allergic to certain foods.  Some people don’t eat certain foods for ethical reasons.  These people still need to eat a balanced diet.

    Investigate one of the following diets:
    a)  Vegan
    b)  Vegetarian
    c)  Celiac
    d)  Lactose intolerant
    e)  Diabetic

    Answer the questions based on the diet you choose to investigate.
    a)  What foods are excluded (not eaten) on this diet?
    b)  What nutrients are these foods (in part a) a major source of?
    c)  Give a suggestion for what foods could be eaten instead of those in part a) so that people on this diet would still have a balanced diet.

  5. Finished?  Need more to do?  Explore BrainPop for other videos on digestion and nutrition.  If you find a good one, share it with the class!

 

 

Grade 7 Science Cover Period 7 & 8

I’m so sorry because I know that you are all excited about the eyeball dissection but I’m sick today so we will do it next lesson.  I don’t want to scare your cover teacher!

Here is what to do today…

Eyes

  1. Open brainpop through your google account (9 dots in the corner!)
  2. Watch the brainpop video called “Eyes”.
  3. Take the quiz and send the results to me in the spreadsheet.  Do not choose to email me.
  4. Repeat the quiz until you have a minimum of 80%.

Light videos by Shea

Choose one of the videos below to watch with a partner.  You can watch more than one if you want.

   

Discuss the video you watched with your partner.  Do you both understand it?  If not, talk about it with someone else that watched it or watch it again and discuss the tricky bits.

For one of the videos, write a blog post summary of the video.  Your summary should include:

  • the main idea(s) from the video – what did you learn?
  • a picture/graphic that you found that is also about that idea and helps explain it