Jmol-Application/C4/Symmetry-and-Point-Groups/English-timed

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Time Narration
00:01 Welcome to this tutorial on Symmetry and Point Groups in Jmol.
00:06 In this tutorial, we will learn to:
00:08 Draw line, that is, axis through atoms in a molecule.
00:12 Spin and rotate the molecule along the axis.
00:17 Draw plane through atoms in a molecule.
00:21 And demonstrate point group classification.
00:25 To follow this tutorial, you should have knowledge of undergraduate Chemistry and familiar with operations from Jmol window.
00:35 If not, for relevant tutorials, please visit our website.
00:39 To record this tutorial, I am using:
00:42 Ubuntu Operating System version 14.04
00:46 Jmol version 12.2.32
00:50 Java version 7 and * Mozilla Firefox browser 35.0.
00:57 Often, symmetry in molecules is described in terms of symmetry elements like:
01:03 Axis of symmetry
01:05 Plane of symmetry Center of symmetry etc.
01:09 We will use Jmol to display these symmetry elements in a molecule.
01:14 Let us begin this tutorial by drawing C3 rotational axis through atoms in a model of methane.
01:22 I have already opened the Jmol window.
01:25 Click on modelkit menu to get the ball and stick model of methane on the panel.
01:31 Label the atoms in the methane molecule by using Display menu in the tool bar.
01:37 Click on Display, scroll down to Label and click on Number option.
01:43 All the atoms in the methane molecule are now numbered.
01:47 We need to write commands in the console to draw lines and planes through atoms.
01:53 To open the Console, click on File menu.
01:57 Scroll down to Console and click on it.
02:01 The Console window opens on the screen.
02:04 We will use draw keyword in the command line to draw lines and planes.
02:10 Detailed information on Jmol script commands is available at this website.
02:15 Open the website in any web browser.
02:19 A web-page opens with a list of keywords used for writing script commands in Jmol.
02:26 Scroll down and click on the word draw in the list.
02:31 A page opens with details about the draw keyword.
02:36 A general syntax for the draw command is given at the top of the page.
02:42 This is followed by information regarding the use of the keyword.
02:47 Let us now go back to the Jmol panel.
02:51 I am using Kmag screen magnifier to magnify the console window.
02:55 To draw a line that represents C3 rotational axis,
02:59 type the following command at the dollar prompt, in the console.
03:04 The command line begins with the word “draw”, followed by object ID.
03:10 Number 250 in the command line refers to the length of the line.
03:15 This is followed by the position of the line.
03:18 Within brackets, atom number equal to 1 and atom number equal to 2. Press Enter.
03:26 Observe the panel.A line passing through atoms 1 and 2 is drawn on the model of methane.
03:33 This line can now act as an axis for rotation.
03:37 We can draw more than one line on a given model.
03:41 To draw C2 rotational axis, type the following command in the console.
03:47 In this command, the numbers in the curly brackets indicate the Cartesian coordinates for the line
03:54 followed by a command to specify the color of the line. Press Enter.
03:59 Now, on the panel, we have methane with C2 and C3 rotational axes.
04:05 To rotate along the line 1, that is C3 axis, type the following command:
04:12 rotate $line1 60 (rotate space dollar line1 space 60).
04:18 The number 60 refers to the degrees of rotation. Press Enter.
04:24 Observe the rotation along line1.
04:27 To spin the molecule along line1, type the following command:
04:32 "spin $line1 180 60" (spin space dollar line1 space 180 space 60).
04:39 The number 180 refers to degrees of rotation and 60 refers to the speed of rotation. Press Enter.
04:48 On the panel, we see the methane model spin along line1, that is C3 axis.
04:55 As an assignment-Draw line representing C3 axis of symmetry, in a model of ethane
05:02 and spin the model along C3 axis.
05:06 Back to the Jmol panel.
05:08 We can also draw planes going through a set of atoms in a molecule.
05:12 To do so, first delete the lines on the methane model by typing the following command.

"draw off" (draw space off). Press Enter.

05:24 To draw reflection plane going through atoms 1, 2 and 3 of the methane molecule:
05:31 type the following command in the console.
05:35 Number 300 in the command indicates the size of the plane. Press Enter.
05:41 Observe the reflection plane going through atoms 1, 2 and 3 in the methane molecule.
05:49 To draw a second reflection plane through atoms 1, 4 and 5:
05:55 In the console, press up-arrow key and edit the command as follows.
06:01 Edit plane1 to plane2 and atomno2 to 4 and atomno3 to 5.
06:12 Also, to change the color of the plane, type the following command:
06:17 ";color $plane2 blue" (semicolon color space dollar plane2 space blue). Press Enter.
06:24 On the panel, we see the two reflection planes in the methane molecule.
06:29 Using Jmol, we can also show point group classification for methane as follows.
06:36 Let's clear the planes drawn on methane molecule, on the panel.
06:41 In the console, type: draw off (draw space off). Press Enter.
06:47 To display all the possible symmetry elements for methane: type the following command in the console.
06:54 "draw pointgroup" (draw space pointgroup). Press Enter.
06:59 We see the symmetry elements of methane displayed on the panel.
07:04 To find out the point group classification for methane, type the following command:

"calculate pointgroup" (calculate space pointgroup). Press Enter.

07:14 Td, the point group of methane molecule, is displayed on the console.
07:20 Another classic example for point group demonstration is allene.
07:25 We can draw the structure of allene, on the panel, using the modelkit menu. Or, we can also download the structure of allene from chemical structure database.
07:37 If you are connected to internet- click on the File menu, scroll down to Get Mol and type “allene” in the text-box. Click on OK.
07:48 To display all possible symmetry elements for allene:
07:52 Press up-arrow key at the dollar prompt, on the console, till you get this command:
07:59 draw pointgroup . Press Enter.
08:02 Observe the panel. We see all possible symmetry elements for allene.
08:09 To get the point group classification for allene -
08:12 Again, on the console, press up-arrow key till you get the command "calculate pointgroup". Press Enter.
08:21 The point group classification for allene, that is D2d, is displayed on the Console.
08:28 Similarly, you can download molecules of your choice and calculate their point group.
08:34 Let's summarize. In this tutorial, we learnt:
08:38 To draw lines, that is, C2 and C3 rotational axes through atoms in methane molecule.
08:45 Spin and rotate the molecule along the axis.
08:49 Draw reflection plane through atoms in methane molecule.
08:54 And demonstrate point group classification using examples of methane and allene.
09:01 As an assignment-Draw reflection plane in a model of dichloromethane
09:07 and find out the point group classification for ammonia and benzene.
09:12 This video summarizes the Spoken Tutorial project.
09:15 If you do not have good bandwidth, you can download and watch it.
09:20 We conduct workshops using spoken tutorials and give certificates. Please contact us.
09:27 The spoken-tutorial project is funded by NMEICT, MHRD, govt of India.
09:33 This is Snehalatha from IIT Bombay, signing off.

Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14