Kirsop Labs

Skills development for science students everywhere

Introduction to Curly Arrows

The Curly Arrows application is an online platform for you to practice drawing reaction mechanisms. Simply go to, and select the type of reaction you want to try. The application can be used with any browser on desktops, laptops, tablets and smartphones.

The level of difficulty is suitable for first year undergraduates. If you feel you need some help with any of the reactions, there are notes available for you:

How to use Curly Arrows

Alkenes and Alkynes

Nucleophilic Substitution

Each level begins with an introductory question in which you are shown the product(s) of a reaction. You’re given a choice of several pre-drawn mechanisms, like those shown in Example 1. Select the mechanism you think is appropriate, and drag it to the outlined area on the screen.

Example 1:

Reaction 1


For the test questions, you’ll be given reactants rather than products as shown in Example 2, and a choice of curly arrows to use to complete the reaction mechanism.

Example 2:

Reaction 2


Select the arrows which you think are correct, and drag them to the appropriate positions.

If an arrow is correct, it will turn green. If an arrow is incorrect, it will turn red.

If your answer is wrong but you’re not sure why, press the ‘check’ button Check buttonand a help message will appear.
(Note that colour functionality may not work on all touchscreen devices.)

If all the arrows are green and you think you’ve got the mechanism completely right, press the ‘check’ button to see if you are correct.

A few things to bear in mind

• The tail of the arrow should begin at the original location of the pair of electrons.

• The head of the arrow should point to the destination of the electrons.

• The arrow should always start at a region of relatively high electron density and end at a region of lower electron density, or on an atom with a strong affinity for electrons.

It’s important that you think about the chemistry of the reaction, rather than just dragging and dropping the arrows until it happens to be correct. You won’t learn much if you do this!

Acknowledgement:  Notes provided by Sarah Piggott, KLabs Student Author