The UV maximum absorbance (lambda_max) of benzaldehyde at 242 nm (element_max 15

Question

The UV maximum absorbance (lambda_max) of benzaldehyde at 242 nm (element_max 15000), 282 nm (element_max 1500), and 328 nm (elementof_max 20) were attributed to the ___ ____and__absorption bands, respectively. The strongest IR absorption band of C1CH_2 C(=0)CH_3 was predicted at about ______ while the strongest IR absorption band of CH_5CH_2C(=0)C1 was predicted ______ which were used to distinguish the two compounds. Arrange the following compounds in order of increasing wave numbers of C = O: ______ There are _____ kinds of protons signals in in its^1 H NMR spectrum, and ______ kinds of carbon signals in its^13C NMR spectrum. The^13C NMR spectrum of showed ________ types of C NMR signals. The DEPT 135 showed ___ negative signals and _______ positive signals. The El source of mass spectrometer often gave_ions, while the ESI source often provided_ions.

Explanation / Answer

1. The UV maximum absorbance of benzaldehyde at 242 nm, 282 nm and 328 nm can be attributed to pi-pi*, n-sigma* and n-pi* absorption bands, respectively.

2. The strongest IR absorption band of ClCH2C(=O)CH3 was predicted at about 1705-1725 cm-1 whereaes the strongest IR absorption band of CH3CH2C(=O)Cl was predicted at 1780-1820 cm-1, which was used to distinguish two compounds.

3. Order of increasing wave number is as follows: b<a<c as conjugation reduces bond order more in case of b (extended due to otho-OH group) and lesser in case of a.

4. There are 7 kinds of proton in 1H NMR spectrum and 9 kinds of carbon signals in 13C NMR spectrum.

5. The 13C NMR spectrum of the compounds showed 8 types of 13C NMR signals. The DEPT 135 showed 1 neagtive signal and 4 positive signals.

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