I have four unknown compounds and I need to solve their structures.

Here is some data about each one:

UNKNOWN #1
Iodoform test = positive
Fehling's test = negative
H20 soluble = yes

IR peaks: 1459, 1936, 2963, 3339

UNKNOWN #2
Iodoform test = negative
Fehling's test = positive (red brick precipitate)
H20 soluble = yes (already in aqueus solution)

IR peaks: none given

UNKNOWN #3
Iodoform test = positive
Fehling's test = negative
H20 soluble = yes

IR peaks: 1652, 1767, 1903, 2410, 2659, 2971

UNKNOWN #4
Iodoform test = positive (pale yellow precipitate bottom)
Fehling's test = negative
H20 soluble = yes

IR peaks: 1712, 2123, 2940, 2979, 3416, 3535

Choose unknowns from these structures:

CH2O, C2H6O, C3H6O, C3H8O, C4H8O, C6H12O6

NONE of the unknowns have OH and C=O groups together in the same molecule.

Fehlings test using Cu2O is sensitive to aldehydes Solution 2 is the only one with a positive aldehyde test.

The Iodoform test is positive in the presense of an alcohol or carbonyl on the 2nd carbon.
R-C=0-CH3 or R-CHOH-CH3 (note that R can also be Hydrogen so acetaldehyde and Ethanol will also give positve reactions too).
Unknowns 1,3,4 have this structure within them.

They're all water soluble. Indicating a polar structure.

Unknown#2 a water soluble aldehyde. With a limited palette of structures to pick from.
CH20 Formaldehyde fits these facts
C2H60 ethanol does not (it would have a positive fehling's test)
Methyl-ether does not fit as it's not a formaldehyde
C3H60 propanaldehyde and C4H8O butylaldehyde would also fit the facts.. Formaldehyde would be the most water soluble of the bunch.

Problem #1's IR data.. 3339cm-1 looks like an alcohol. 1936cm-1 seems to be a vinyl group.

Problem#3 1767 indicates a carbonyl.
the peaks listed 1903,2410 and 1652 are important clues. I'm not finding cross references in my books at home.

Problem 4.. Is this a mixture? 1712 is a strong indication of a carbonyl and the 3416,3535 cm-1 indicate an alcohol.. but there is the restricition of the puzzle of -0H and C=O not on the same molecule.