Functional group region

The two important areas for a preliminary examination of a spectrum are the regions 4000-1300 and 900-650 cm-1. The high-frequency portion of the spectrum is called the functional group region. The characteristic stretching frequencies for important functional groups such as OH, NH, and C=0 occur in this... 

If no absorption bands are present in the functional group region, with the exception of those arising from carbon-hydrogen stretching modes, consider the possibilities of ethers, alkyl halides, sulphur compounds, tertiary amines and nitro compounds as detailed in the sections below. 

Infrared spectroscopy is mainly used to tell what types of bonds are present in a molecule (using the functional group region, 1500-5000 cm-1) and whether two substances are identical or different (using the fingerprint region, 700-1500 cm-1). 

Know the meaning of the functional group region and fingerprint region of an infrared spectrum, and tell what kind of information can be obtained from each. 

Both compounds will be similar in the functional group region of the spectrum with bands at 3500 cm-1 for the O-H stretch and 1600-1680 cm-1 for the C=C stretch. Their fingerprint regions (700-1500 cm-1) are expected to differ from one another. 

Chemical group Functional group Region (cm ) Strength... 

The functional group region occurs at > 1500 cm . Common functional groups give one or two peaks in this region, at a characteristic frequency. 

Comparing the functional group region and fingerprint region of two compounds... 

Besides learning the general regions of the IR spectrum, it is also important to learn the specific absorption values for common bonds. Table 13.2 lists the most important IR absorptions in the functional group region. Other details of IR absorptions will be presented in later chapters when new functional groups are introduced. Appendix E contains a detailed list of the characteristic IR absorption frequencies for common bonds. 

Problem 13.14 What are the major IR absorptions in the functional group region for each compound ... 

The functional group region from 4000-1500 cm" is the most useful region of an IR spectrum. 

A solution of acetone [(CH3)2C=O] in ethanol (CH3CH2OH) in the presence of a trace of acid was allowed to stand for several days, and a new compound of molecular formula C7H16O2 was formed. The IR spectrum showed only one major peak in the functional group region around 3000 cm and the NMR spectrum is given here. What is the structure of the product ... 

The IR spectrum in the mid-IR region is divided into the functional-group region, 4000-1300 cm and the fingerprint region, 1300-400 cm. To interpret an IR spectrum, the hydrogen-stretching vibrations. 

Region 2 (2000-1500 cmr1) this is known as the functional group region and includes the stretching frequencies for C=C, C=0, C=N, N=0 and N—H bending vibrations. 

Functional groups Region cm Intensity Infrared Raman Vibration mode... 

The IR spectra of (a) 2-pentanol and (b) 3-pentanol. The functional group regions are very similar because the two compounds have the same functional group, but the fingerprint regions are unique for each compound. 

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