What is the IR frequency for alkane C-H stretching?

The C-H-stretching modes can be found between 2850 and 3300 cm-1, depending on the hydrization. The range from 2850-3000 cm-1 belongs to saturated systems (alkanes, sp3, example 1), while the peaks from 3000-3100 cm-1 indicate an unsaturated system (alkenes, sp2, example 2; aromatic ring, example 3,4).

How can you identify alkane on the basis of IR spectroscopy?

The spectra of simple alkanes are characterized by absorptions due to C–H stretching and bending (the C–C stretching and bending bands are either too weak or of too low a frequency to be detected in IR spectroscopy). In simple alkanes, which have very few bands, each band in the spectrum can be assigned.

What does C-H stretch mean?

Aromatic ring stretching. Alkenes The vinylic hydrogen (=C-H) stretches appear just above 3000 cm-1; they overlap the aromatic C-H stretches. The C=C stretch is medium to non- existent between 1640 and 1670 cm-1.

What is C-H sp3?

sp3 orbital: One of a set of hybrid orbitals produced when one s orbital and three p orbitals are combined mathematically to form four new equivalent orbitals oriented toward the corners of a regular tetrahedron. The resulting C-H bonds point to the corners of a tetrahedron, and have H-C-H bond angles of 109.5o.

How are alkanes spectra characterized in IR spectroscopy?

The spectra of simple alkanes are characterized by absorptions due to C–H stretching and bending (the C–C stretching and bending bands are either too weak or of too low a frequency to be detected in IR spectroscopy).

What is the C-H stretch of alkenes?

This is a very useful tool for interpreting IR spectra: Only alkenes and aromatics show a C-H stretch slightly higher than 3000 cm-1. Compounds that do not have a C=C bond show C-H stretches only below 3000 cm-1. The strongest bands in the spectra of alkenes are those attributed to the carbon-hydrogen bending vibrations of the =C–H group.

Are there any bands on the IR spectrum for alkenes?

Bands for C–H scissoring (1465) and methyl rock (1378) are marked on this spectrum; in routine IR analysis, these bands are not specific to an alkene and are generally not noted because they are present in almost all organic molecules (and they are in the fingerprint region). The bands at 917 cm-1 and 1044cm-1 are attributed to =C&Mac173H bends.

What are the absorptions of a simple alkane?

The spectra of simple alkanes are characterized by absorptions due to C–H stretching and bending (the C–C stretching and bending bands are either too weak or of too low a frequency to be detected in IR spectroscopy). In simple alkanes, which have very few bands, each band in the spectrum can be assigned. C–H stretch from 3000–2850 cm-1