organic salts (RCO2-Na+ & NR4+Cl-)	saturated hydrocarbons
monofunctional alcohols (ROH)	unsaturated hydrocarbons
esters (RCO2R')	aromatic hydrocarbons
ethers (ROR')	alkyl halides
acids (RCO2H)	aryl halides
amines (NR3)
nitriles (RCN)
amides (RC(O)NH2)
ketones (RC(O)R')
aldehydes (RCHO)
etc...(all less than five carbons)

Notes:

1. A compound is deemed "soluble" in water if it dissolves to the extent of 3.3 g / 100 mL of water.
   
   
2. In most homologous series of the above types of compounds, the longest chain with appreciable water solubility will be reached at about five carbons.



3. Introduction of a halogen will usually lower the solubility.



4. A benzene ring approximates 4 aliphatic carbons.



5. Position of functional group, branching, and the compactness of the molecule will affect solubility:



• functional group toward center of molecule - increased water solubility



• increase in the number of branches - increased water solubility



• more compact molecular shape - increased water solubility