S3.2.9 Infrared spectroscopy (HL)

[@12345whoscounting]

Hi, Thanks for the video. Where is the reference to the absorption of IR by greenhouse gases

[@EukkMaruSpeedrun]

Thanks for the good video! I have a question, though. In the data booklet, the wavenumber for iodoalkanes (C-I) is 490-620 cm^-1, which is a fingerprint region (500~1500 cm^-1), not a functional group region. Aren't we supposed to only look at functional group region to identify the bonds? If the given data from the data booklet is in the fingerprint region, how are we supposed to identify them?

[@Emkeys-i1v]

No idea. Good question

[@mohsenhajian6303]

thank you very much for your instructional and useful video, I am confused if only polar bonds can be detected in FTIR, how C-C bond can be detected since it is a non polar

[@acnaji]

Thank you Just one question, what about when in the intensity column, it says 'broad' and 'very broad', etc?

[@MSJChem]

+Abdullah Naji Infrared bands come in various shapes, the most common being narrow and broad. Narrow bands are thin and pointed, broad bands are wider and smoother. A typical example of a broad band is that displayed by OH bonds, such as those found in alcohols and carboxylic acids. If you are interested, you can find more information here, at the bottom of page. www.chem.ucla.edu/~webspectra/irintro.html

[@dhvaniagrawal2319]

At 2:26, how do we find out how many carbon atoms are there in the compound?

[@MSJChem]

Dhvani Agrawal An IR spectrum will not tell you directly how many carbon atoms there are in the compound. It will tell you the type of bonds in the molecule. Remember that you use a variety of techniques to find the identity of the molecule, such as mass spectrometry, H NMR, etc.

[@dhvaniagrawal2319]

@@MSJChem Okay. Thank you so much.

[@shamelsinha1626]

Hey thanks for the video. Going through the past paper, I noticed a question about plastic identification codes like LDPE and HDPE which required me to use section 30 of the databooklet and some other info that I haven't learned before. Is this required for the new syllabus?

[@MSJChem]

Are you sitting the May 2022 exams?

[@shamelsinha1626]

@@MSJChem Yes I am

[@MSJChem]

@@shamelsinha1626 Plastics are covered in option A so you do not need to know the difference between LDPE and HDPE.

[@mukundnarasimhan4865]

thank you

[@TasFirinErkegi]

is this hl or sl

[@MSJChem]

It’s HL for the 2025 exams.