GChemPaint/C3/Resonance-Structures/English-timed

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Title of the tutorial: Resonance Structures

Author: Madhuri Ganapathi

Key words: Show Electron shift and Resonance Structures, Create a reaction pathway, Create a mesomeric pathway, Build Retrosynthetic Pathway, Video tutorial.

Time Narration
00:01 Hello everyone.
00:02 Welcome to this tutorial on Resonance Structures in GChemPaint.
00:06 In this tutorial, we will learn to,
00:09 * Use different types of arrows to represent chemical reactions and
00:14 * Add charge and electron pairs on an atom
00:18 For this tutorial I am using
00:20 Ubuntu Linux OS version 12.04.
00:24 GChemPaint version 0.12.10.
00:29 To follow this tutorial you should be familiar with GChemPaint.
00:34 If not, for relevant tutorials, please visit our website.
00:39 I will switch to GChemPaint window.
00:42 I have opened a new GChemPaint window.


00:45 Here you can see EthylChloride and Methylbromide structures.
00:50 I will show how to obtain a Carbo-cation.
00:55 Let's add a pair of electrons on the Chlorine atom of EthylChloride.
01:01 Click on Add an electron pair tool.
01:04 Click on Chlorine atom and observe what happens.
01:09 Next, I will show an electron pair shift in the Carbon-Chlorine bond.
01:14 Click on Add a curved arrow to represent an electron pair move tool.
01:18 Property window opens.
01:21 Click on End arrow at center of new bond check box.
01:26 It moves the electron pair to the correct position.
01:30 Click on Carbon-Chlorine bond.
01:33 Place the cursor on the curved arrow and observe the electron shift.
01:39 I will make the copy of this structure.
01:42 Now, click on Add an arrow and click between the structures.
01:48 Formation of a Carbo-cation is initialized by a base like Sodium Hydroxide(NaOH).
01:54 Click on Add or modify a group of atoms tool, click above the arrow.
02:00 Type NaOH.
02:04 Click on Selection tool and select NaOH.
02:09 Right-click on the arrow.
02:12 In the submenu, select Arrow.
02:13 Click on Attach selection to arrow.
02:18 A dialogue box with heading Arrow associated appears.
02:23 In the Role drop-down, select “Reactant” and click on Close.
02:29 Now, let's convert second EthylChloride to Ethyl Carbo-cation and Chloride ions.
02:36 Click on Eraser tool and click on Carbon-chlorine bond.


02:42 Ethane(CH3-CH3) and HCl are formed.
02:45 When electrons shift from Carbon to Chlorine, Carbon gains a positive charge.
02:51 Click on Increment the charge tool.
02:54 Click at the position from where Carbon-chlorine bond was deleted.
02:59 Ethyl Carbo-cation(CH3-CH2^+) is formed.
03:02 To form Chloride ion, click on Decrement the charge tool.
03:07 Click on HCl. Chloride(Cl^-) ion is formed.


03:12 Now let's move to single electron shift.
03:15 Let's use the Methylbromide structure to obtain free radicals.
03:20 Click on Add a curved arrow to represent a single electron move tool.
03:26 Click on Methylbromide bond to obtain a curved arrow.
03:30 Shift the Pencil tool a little on the bond, click again to get second curved arrow.
03:38 One arrow moves to bromo(Br) and other arrow moves towards methyl(CH3).
03:44 Both Bromo(Br) and methyl(CH3) will get one electron each from the bonded pair of electrons.
03:51 To show the products, let us add an arrow.
03:54 Click on Add an arrow, click on Display area beside Methylbromide.
04:00 Formation of free radicals involves heat in the reaction.
04:04 Click on Add or modify a text tool.
04:08 Click on the Display area above the arrow.
04:11 Type “Heat” in the green box.
04:14 Click on Selection tool and select “Heat”
04:19 Right-click on the arrow.
04:21 In the Submenu select Arrow and Click on Attach selection to arrow.
04:27 A dialogue box with heading Arrow associated appears.
04:32 Notice that Role drop down list has more options.
04:37 In the Role drop-down, select “Temperature” and
04:40 click on Close.
04:43 Now let's create the free radicals.
04:46 I will make a copy of this structure.
04:50 Click on Eraser tool and click on Carbon-bromine bond.
04:55 Methane(CH4) and Hydrogen-bromide(HBr) are formed.
04:59 Click on Add an unpaired electron tool.
05:02 Click on Methane(CH4) and Hydrogen-bromide(HBr)
05:06 Methyl(CH3) and Bromium(Br) free radicals are formed.
05:10 Click on Selection tool.
05:12 To create a reaction pathway, first select the complete reaction.
05:17 Now, right-click on the selection.
05:20 A submenu opens.
05:22 Click on Create a new reaction.
05:25 Reaction path is created.
05:28 Drag to see the reaction pathway.
05:30 Likewise, I will create the reaction pathway for the previous reaction.
05:37 We can also remove the reaction pathway, if we want to.
05:41 To do so, right-click on the reaction again
05:45 Click on Destroy the reaction.
05:48 This action will remove the reaction pathway.
05:51 Drag any of the objects, and you will see that they can be moved individually.
05:57 Now we move on to Resonance or Mesomery using double headed arrow.
06:02 I have opened a new GChemPaint window with structures of Nitromethane.
06:08 I had added curved arrows and charges to show electron shifts within the structures.
06:14 Now let's add a double headed arrow.
06:16 Click on Add a double headed arrow.
06:20 Click on the Display area in between Nitromethanes.
06:25 The two structures are "Resonance structures" of Nitromethane..
06:30 Press CTRL+A to select the structures.
06:33 Right-click on the selection.
06:35 A submenu opens.
06:37 Click on Create a new mesomery relationship.
06:41 Drag to see the relationship.
06:44 Here is slide for the Resonance Structures of Benzene.
06:48 Now, let's learn to create a retro-synthetic pathway.
06:52 I have opened a new GChemPaint window with the required structures.
06:57 Retrosynthetic pathway starts with the product and goes to the reactant
 along with all the intermediates.
07:04 In this pathway, the final product is Ortho-nitrophenol and the starting material is Benzene.
07:10 Let us add a retro-synthetic arrow, to show the retro-synthetic pathway.
07:15 Click on Add an arrow for a retrosynthetic step.
07:20 Click between all the compounds.
07:25 Press CTRL+A to select the structures.
07:28 Right click on the selection.
07:30 A sub-menu opens.
07:32 Click on Create a new retrosynthesis pathway.
07:36 Drag to see the created pathway.
07:39 Let's summarize what we have learnt.
07:41 In this tutorial we have learnt to
07:44 * Show electron shifts using curved arrows
07:48 * Attach reaction conditions to reaction arrows.
07:52 * Create and destroy reaction pathway using a reaction arrow
07:57 * Create a new mesomery relationship using double headed arrow
08:01 * Create a retro-synthetic pathway using retro-synthetic arrow.
08:06 As an assignment
08:07 Using arrow properties
08:10 1. Create a reaction pathway for the reaction of Bromo-Ethane (C2H5Br) and Sodium(Na) with solvent Dryether to get Butane & Sodiumbromide.
08:20 2. Add stoichiometric coefficients to reaction molecules.
08:24 3. Draw resonance structures of Naphthalene, Anthracene and Carbon-dioxide
08:30 This is the required reaction pathway.
08:33 These are the resonance structures of Naphthalene, Anthracene and Carbon-dioxide.
08:39 Watch the video available at this URL.

http://spoken-tutorial.org/What_is_a_Spoken_ Tutorial

08:43 It summarizes the Spoken Tutorial project
08:45 If you do not have good bandwidth, you can download and watch it
08:50 The Spoken Tutorial Project Team Conducts workshops using spoken tutorials
08:54 Gives certificates to those who pass an on-line test
08:57 For more details, please write to contact@spoken-tutorial.org
09:03 Spoken Tutorial Project is a part of the Talk to a Teacher project
09:08 It is supported by the National Mission on Education through ICT, MHRD, Government of India


09:16 More information on this Mission is available at this link

http://spoken-tutorial.org/NMEICT-Intro]

09:21 This is Madhuri Ganapathi from IIT Bombay signing off. Thank you for joining.


Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14