For each spectrum, interpret all the significant streching frequencies above 1580 cm^-10

For each spectrum all the significant stretching frequencies above 1580 cm^-1 are given.

First spectrum:

1642 cm^-1 : C=N stretching frequency in imine or oxime.

2900 cm^-1: C-H stretching frequency in an alkane.

Second spectrum:

1626 cm^-1: C=C stretching frequency in cis disubstituted alkenes.

1691cm^-1: C=O stretching frequency in primary amide.

2712 cm^-1: C-H stretching frequency in aldehyde as it is in the range of 2830-2695 cm^-1

2814 cm^-1: C-H stretching frequency of alkane.

Third spectrum

1650 cm^-1: Free associated C=O .

1703 cm^-1: C=O stretching frequency in aliphatic ketone.

2935 cm^-1: C-H stretching frequency in alkane as it is in the range of 3000-2840 cm^-1.

1604 cm^-1: C=C stretching frequency in alpha, beta-unsaturated ketone.

Fourth spectrum

1742 cm^-1: C=O stretching frequency in aldehydes.

3050 cm^-1: C-H stretching frequency in alkane.