phenol + h2o

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    3986
  • This page looks at the structure and physical properties of phenol (very old name: carbolic acid). Phenol is the simplest thành viên of a family of compounds in which an -OH group is attached directly vĩ đại a benzene ring.

    The structure of phenol

    The simplest way vĩ đại draw the structure of phenol is:

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    phenol.gif

    . . . but vĩ đại understand phenol properly, you need vĩ đại dig a bit deeper than thở this.

    There is an interaction between the delocalized electrons in the benzene ring and one of the lone pairs on the oxygen atom. This has an important effect on both the properties of the ring and of the -OH group. One of the lone pairs on the oxygen overlaps with the delocalized ring electron system . . .

    phenoldeloc1.gif

    . . . giving a structure rather lượt thích this:

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    phenoldeloc2.gif

    The donation of the oxygen's lone pair into the ring system increases the electron mật độ trùng lặp từ khóa around the ring. That makes the ring much more reactive than thở it is in benzene itself. That is explored in another page in this phenol section. It also helps vĩ đại make the -OH group's hydrogen a lot more acidic than thở it is in alcohols. That will also be explored elsewhere in this section.

    Physical properties

    Pure phenol is a white crystalline solid, smelling of disinfectant. It has vĩ đại be handled with great care because it causes immediate white blistering vĩ đại the skin. The crystals are often rather wet and discolored.

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    Melting and boiling points

    It is useful vĩ đại compare phenol's melting and boiling points with those of methylbenzene (toluene). Both molecules contain the same number of electrons and are a very similar shape. That means that the intermolecular attractions due vĩ đại nài der Waals dispersion forces are going vĩ đại be very similar.

    melting point (°C) boiling point (°C)
    C6H5OH 40 - 43 182
    C6H5CH3 -95.0 111

    The reason for the higher values for phenol is in part due vĩ đại permanent dipole-dipole attractions due vĩ đại the electronegativity of the oxygen - but is mainly due vĩ đại hydrogen bonding. Hydrogen bonds can khuông between a lone pair on an oxygen on one molecule and the hydrogen on the -OH group of one of its neighbors.

    Solubility in water

    Phenol is moderately soluble in water - about 8 g of phenol will dissolve in 100 g of water. If you try vĩ đại dissolve more than thở this, you get two layers of liquid. The top layer is a solution of phenol in water, and the bottom one a solution of water in phenol. Phenol is somewhat soluble in water because of its ability vĩ đại khuông hydrogen bonds with the water.