FTIR - Functional Groups & Frequencies

Bookmarking this page can allow students access to these resourses after our semester ends and Canvas accounts are no longer accessible.

• Sound Mute tab functionality in Firefox (click here) while 'looking for clues' in learning infrared spectroscopy. (Song "Looking for Clues" by Robert Palmer)

There are multiple aspects to this course activity: learning the theory behind FTIR active stretching and bending frequencies; memorizing our stretching frequencies; how to prepare a sample for analysis; how to interpret an FTIR spectrum and how to correctly word process infrared data in writing a laboratory report for this experiment. These key aspects to FTIR spectroscopy are summarized below:

• All topics below are covered in the playlist (click here).
• IMPORTANT - Our audio-tutorials presented in this couse activity do not presume to cover all aspects of infrared spectroscopy and are optional. Students are strongly encouraged to be engaged in reading the appropriate chapter in their laboratory textbook as they prepare their study guide on infrared spectroscopy. Additionally, our companion lecture course textbook has further resources to be studied in learning about the content presented on this page and on subsequent pages in this module. The learning process in our course is based on the belief that everyone has the capacity to broaden one’s knowledge and their understanding of methods of gaining knowledge in chemistry and to develop one’s abilities in critical thinking, in oral and written communication, and in mathematics. This includes increasing the range of one's knowledge, understanding, or experience by looking up additional resources as a responsible student.
• CHEM231L is a companion course to CHEM231. In laboratory, spectroscopy is scheduled and taught in laboratory (6 hours of course time devoted to it). Later, we will have 6 hours scheduled laboratory time for nuclear magnetic spectroscopy (NMR). As we approach the end of CHEM231, these concepts of spectroscopy (IR and NMR) learned in laboratory are applied concepts, chemical reactivity and outcome discussed in the last eight weeks of CHEM231, reviewing spectroscopy taught in laboratory in lecture as needed.

Learning Basic FTIR Theory

• Preparatory reading of our textbook on the concept of infrared spectroscopy—and lecture textbook or by from a virtual textbook as needed—can help students in being better engaged in this course activity as one prepares a study guide on spectroscopy.
• Begin by reviewing the basics of infrared radiation as electromagnetic radiation (click here), and
• Complete Page 63 linked below on the DAY 1 for this course activity, and begin to complete our problem-set laboratory manual pages 63-75.
• Infrared theory and the technique is taught during the schedule laboratory periods for this course activity, and the technique with spectral interpretation is applied throughout the semester going into next semester moving forward.

Memorizing IR stretching frequencies

• The stretching frequencies presented in our course are "generic" numerical values and ranges.
• Completing page 63 from our supplemental packet by following along with the silent movies can provide a list of generic infrared stretching values needed in future course activities (i.e, drill & practices, assessments) (click here) while being more engaged in preparing a study guide on infrared spectroscopy.
• Use the "generic" numerical values and ranges from the student prepared list on page 63 (click here) in completing the infrared problem-set.

NOTE: page 63 in our supplemental packet summarizes generic stretching frequencies needed for our course when looking for IR clues in determining functionality (functional group) for a given molecule. Our laboratory manual contains supplemental materials (e.g.; data tables, spectral problem-set, etc.) in support of our course activities and dose not presume to cover all aspects of infrared spectroscopy.  Students are strongly encourage to be engaged in reading their laboratory textbook as they prepare their study guide over infrared spectroscopy while being engaged in supplemental materials in support of our course activities and optional content like looking up further resources while pursuing by their own self-directed study.

Learning stretching frequencies associated with functional groups should be our focus.

• Knowing the difference between a stretching and a bending is important.
• Stretching frequency value (wave number) > Bending frequency value (wave number), and stretching frequencies are more intense in absorption than bending.
• Learning stretching frequencies (wave number) associated with functional groups should be our main focus. Only a few bending modes with bending frequencies are need to be learned this semester.
• Stretching modes are intense and are higher in energy—it takes more energy to stretch than to bend bonds.
• Learning our stretching frequencies is far more important than learning the few bending frequencies this semester.

Conjugation, Overtones & Bending Modes

• This audio-tutorial reviews the ideas for Conjugation, Overtones & Bending Modes (click here).
• Bending modes are less intense than stretching modes and are less important to us when interpreting FTIR spectra than stretching modes.
• There are less than five bending frequencies students need memorize unlike the large number of stretching modes.

IR Stretching Frequencies - An Overall Summary (click here)

FTIR Problem Set available

• After completing the FTIR problem-set in our laboratory manual, answers the questions are inputted into Canvas.
• Work collaboratively as students in answering questions in the problem-set.

FTIR Report

• Correctly formatting spectral data in our course is important word processing skill to be applied in presenting spectral data in our reports this semester and beyond. To learn how (click here).
• Please keep me posted of your progress and emailing me your questions or if you need help.
• Preparing a list of questions and bringing them to our course period, or to my attention, can keep students more engaged in this course activity.
• Like we have been doing this semester, please continue to use an appropriate subject headng course identifier (i.e., CHEM231L - IR help) to dgergens@sdccd.edu when emailing for prompt replies.