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Hydrophobic and hydrophilic

  1. Jun 24, 2006 #1
    What are examples of molecules that include both hydrophilic and hydrophobic groups?
    Does this mean surfactants and amphiphiles ? Or are those the same?

    Thank you.
  2. jcsd
  3. Jun 24, 2006 #2
    Water is hydrophillic ( mixes with water easily ) and oils or fats are generally hydrophobic. It may seem obvious but the idea of water being hydrophillic gives you an idea of why, like dissolves like and water-like substances tend to be hydrophillic because they bond and interact with water. For example, salts will dissolve in water because theyr ionic and the nature of water as dipole/solvent. So substances with electronically charged groups, polar/high dipole moments tend to be more hydrophillic.

    On the other hand, oils and covalently bonded long chain hydrocarbons are bulky and lack the charge seperation that makes them easily soluble in aqueous solutions. They are hydrophobic and seperate out from water, forming an oily layer.

    Some larger molecules exhibit both these properties, perhaps having charged electronegative groups on one end and a long branch of alkanes at the other. This is has a tendancy for one side of the molecule to align to favour the solvent.

    Surfactants are compunds that alter the properties of the solvent in favour of its opposite property, by virtue of having a group or region that exhibits both properties. They form "bubble-like" structures around non soluble substances which i think is related to amphiphiles, though im not very familiar with it.
  4. Jun 25, 2006 #3


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    Amphiphiles are what you are looking for, they are molecules with both hydrophobic and hydrophilic sections. Surfactants are a subset of of amphiphiles; surfactants reduce water tension by adsorbing to the water at the air-water interface. If you are looking for examples of amphiphiles, 3trQN has given you some, for further examples you need look no further than biology. Most biological molecules are amphiphiles, phospholipids for example which form the main part of your cell membranes are amphiphiles; most lipids are amphilphiles, fatty acids (CH3(CH2)nCOOH) are amphiphiles. Basically, when you are identifying amphiphilic molecules you should be looking for a polar section and a non-polar section(usually a long hydrocarbon chain), the polar section does not necessarily have to be ionic.
    Last edited: Jun 25, 2006
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