May 2022 IB Chemistry HL IA (22/24)

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이 문서는 2022년도 May Session을 위해 작성했던 Internal Assessment이며, Chemistry HL이고 최종 점수 22/24 이었습니다. Data-Based IA이고 Effect of Increasing Carbon Chain Length of Alcohols and Methyl Esters on the Infrared Spectra 이라는 주제로 진행한 IA입니다.

 

[본문내용]

Effect of Increasing Carbon Chain Length of Alcohols and Methyl Esters on the Infrared Spectra

Introduction

When I first came across the infrared spectrum in section 26 of the IB Chemistry Data Booklet, I saw that the characteristic ranges provided for each bond were extremely vague – for instance, the O-H bond in carboxylic acids would have a wavenumber of 2500–3000 cm-1, with a “strong [and] very broad” intensity (International Baccalaureate). This lack of detailed information sparked my interest and made me question in what ways increasing carbon chain length in a homologous series would impact the intensities of the peaks in the infrared spectra, as they contain the same functional group and therefore the same types of bonds.

Background Information

Infrared (IR) spectroscopy is a common technique used to determine the functional groups present in a sample. This technique involves infrared radiation, which is a part of the electromagnetic spectrum with wavelengths between 780 nm and 1 mm (C.P.S. Hsu). The transmittance IR spectrum is usually presented with the wavelength or wavenumber (cm-1) as the x-axis and the % transmittance as the y-axis (Figure 1).

Transmittance IR spectroscopy involves passing infrared radiation through the sample and detecting the % transmittance, which indirectly shows the absorption of radiation at each wavelength (Ye and Spencer). As infrared light has less energy than ultraviolet and visible light, it cannot excite electrons, but can cause vibrations in covalently bonded molecules (JASCO Global). Hence, as samples absorb some of the radiation that passes through, only some of the radiation is transmitted. Due to the different functional groups in the samples, each compound will interact with the infrared light differently, thus yielding different spectral features. For instance, methanoic acid contains the carboxyl functional group. Due to the characteristic of the functional group, its spectrum shows a strong peak at a wavenumber of around 1720 cm-1, which corresponds to the transmittance characteristics of the C=O double bond in carboxylic acids (Figure 1)…

 

  • 총 페이지수: 12 pages
  • 과목명: Chemistry
  • 주제: Effect of Increasing Carbon Chain Length of Alcohols and Methyl Esters on the Infrared Spectra
  • The file is in PDF format.
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May 2022 IB Chemistry HL IA (22/24)

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