The functional groups in an organic compound can frequently be deduced from its

Question

The functional groups in an organic compound can frequently be deduced from its infrared absorption spectrum. A nitrogen-containing compound exhibits a brodened absorption at 3400 cm(m) but no absorption in the 2200, 1630-1820, or 1000-1250 cm regions. Relative absorption intensity: (s)-strong, (m)-medium, (w) weak. What functional class(es) does the compound belong to? Do not over-interpret exact absorption band positions. None of your inferences should depend on small differences like 10 to 20 cm The functional class(es) of this compound is(are List only classes for which evidence is given here. Attach no significance to evidence not cited explicitly Enter letters from the table below, in any order, with no spaces or commas a. alkane (List only if no other functional class applies.) b. alkene e. terminal alkyne d. internal alkyne e. arene . alcohol g. ether h. amine i. aldehyde or ketone j. carboxylic acid k. ester L nitrile Submit Answer Retry Entire Group 9 more group attempts remaining

Explanation / Answer

1) The broadened absorption at 3400 cm-1 suggests an amine, it shouldn't be an aromatic amine because the flexions at 1225-950 cm-1 are absent. For a nitrile there must be present at least one absorption at 2210-2260 cm-1 but this is not the case. We can conclude we have an aliphatic amine. [Ans. h. ]

2) The intense absorption at 1715 cm-1 corresponds to a carbonyl group, if it were of a carboxylic acid, we should see an absorption in 3000-2200 cm-1 and two more in 1420-1200 cm-1, for an esther there should be two absorptions in 1300-1050 cm-1 ,so the only available options are aldehyde or ketone. Ketone should have small absorptions in 1100-1300 cm-1 , so the compund must be an aldehyde which must have two signals in 2900-2800 cm-1 and 2775-2695 cm-1 , this are allowed by the problem. [Ans. i. ]

3) Alcohols present strong, broad absorptions above 3600 cm-1 and primary alcohols present an absorption around 1050 cm-1 .It's a primary alcohol. [Ans. f. ]

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