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We have 3 modes of learning for students to choose from: weekly physical classes at Bishan; weekly online lessons via Zoom; and on-demand video lessons.

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Please be rest assured that I conduct all my classes personally and I do not engage other tutors to teach at my centre.

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Most of my students showed improvements by at least 3 grades and more than 80% have attained distinction for A Levels. The earlier the students join my classes, the more confident I am in improving their grades.

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Usually the class size is around 10 to 12 students. Max class size is 16 pax.

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Yes makeup lesson is available in the same week subject to availability. If makeup class is not possible, the student can view the recorded video lessons at Google Classroom.

Do you have trial lesson available? How much is it?

Yes we do. Fees for trial lesson are for Bishan class and for Zoom online class.

Does your centre offer O Level chemistry tuition? Do you teach IB / IP chemistry tuition? How about H1 Chemistry?

Chemistry Guru specialises in H2 Chemistry for JC1 and JC2 or IP Year 5 and IP Year 6 students only. Find out all the information about A Level H2 Chemistry and the detailed comparison between H1 and H2 Chemistry. We do not conduct lessons for H1 Chemistry, O Level Chemistry, IB Chemistry or IP Chemistry at IP Year 3 and IP Year 4.

Predict Number of Monosubstituted Products for Free Radical Substitution

Hi folks! This is my first video for 2019 and I would like to wish everyone a great and fruitful year ahead!

In this video created by Chemistry Guru, Singapore's leading JC Chemistry tuition centre, we want to discuss how to determine the number of monosubstituted products when an alkane undergoes free radical substitution.

We also want to estimate the expected ratio of these products.

We will be using 2 alkanes for examples: butane and 2-methylbutane.

Let us take a look at the first example butane:

The first thing is to determine the number of products when butane undergoes monosubstitution.

What we need to consider is this:

How many different types of carbon are there in this alkane?

predict products FRS how many different types of carbon

From the structure of butane we can find 2 different types of carbon.

predict products FRS butane structure

So therefore we would expect 2 different monochloroalkane products: 1-chlorobutane and 2-chlorobutane.

predict products FRS chlorobutane products

Next we want to determine the ratio of these products.

Assuming the likelihood of substitution at each C-H bond is the same, we can then use probability to predict the ratio.

So what we focus on next is this:

How many C-H bonds are there for each type of carbon?

predict products FRS how many C H for each carbon

By looking at the structure of butane, we can determine that substituting 6 C-H (blue) for Carbon-1 will form 1-chlorobutane and substituting 4 C-H (yellow) for Carbon-2 will form 2-chlorobutane.

So the ratio between 1-chlorobutane and 2-chlorobutane will be 6:4 or 3:2.

Let's consider the second example 2-methylbutane.

predict products FRS 2 methylbutane example

There are 4 different types of carbon so there will be 4 monosubstituted products.

The number of C-H bonds for each type of carbon are listed below:

Carbon-1 has 6 C-H bonds (yellow)
Carbon-2 has 1 C-H bond (pink)
Carbon-3 has 2 C-H bonds (blue)
Carbon-4 has 3 C-H bonds (green)

So therefore the ratio of monosubstituted products 1, 2, 3 and 4 will be 6:1:2:3.

For the detailed step-by-step discussion on how to determine the number of free radical substitution products and their ratio, check out this video now!

Topic: Alkanes, Organic Chemistry, A Level Chemistry, Singapore

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