What specific IR absorption peaks should be found for caffeine?
The caffeine FTIR spectrum showed the characteristic two peaks of the vibrations of the C-H (2950-2850 cm −1 ) methyl groups [37]. This asymmetric vibration enables the quantitative analysis of caffeine in extractives of coffee beans or tea leaves [38] .
Which functional group shows absorption at highest IR frequency?
Group Frequencies – a closer look
| Stretching Vibrations | ||
|---|---|---|
| Functional Class | Range (cm-1) | Intensity |
| Alkanes | 2850-3000 | str |
| Alkenes | 3020-3100 1630-1680 1900-2000 | med var str |
| Alkynes | 3300 2100-2250 | str var |
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).
Why does the IR spectrum of caffeine contain two carbonyl peaks?
The IR spectrum of caffeine contains two carbonyl peaks because caffeine is made up of two different carbonyl groups. Both peaks are due to an amide, with one amide frequency being higher than the other.
What functional groups are in caffeine?
The functional groups in caffeine are amine and amide.
Which IR frequency are absorbed by compound?
Since most organic compounds have C-H bonds, a useful rule is that absorption in the 2850 to 3000 cm-1 is due to sp3 C-H stretching; whereas, absorption above 3000 cm-1 is from sp2 C-H stretching or sp C-H stretching if it is near 3300 cm-1.
What is the IR frequency for CIS alkene C-H bending?
The C-H wags of alkenes fall in a similar range, between 1000 and 600. To summarize then, the IR spectra of alkenes are characterized by one or more C-H stretching peaks between 3100 and 3000, a possible C=C stretch from 1680 to 1630, and one or more C-H wagging peaks from 1000 to 600.
What procedure involving your isolated caffeine sample might be used to get caffeine that exhibits a melting point closer to the literature value?
sublimation) to get caffeine that exhibits a melting point closer to the literature value? method could be used to isolate a pure crystal form of caffeine, free from any impurities.
What procedure involving your isolated caffeine sample might be used other than sublimation to get caffeine that exhibits a melting point closer to the literature value?
simple distillation
If you do not want to use sublimination another option is to use fractional or simple distillation to get a more pure isolllate the caffeine which would exhibit a melting point closure to the literature value.