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What do we mean by the following in organic chemistry? watch

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    In organic chemistry, I came along the following notes:

    Homologous series of alkanes
    Alkanes are saturated organic compounds
    Homologous series of alkenes
    Alkenes are unsaturated organic compounds

    Can you just describe the bold-italic words?

    Thanks.
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    Organic chemistry? Isn't that biology.
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    (Original post by SWEngineer)
    In organic chemistry, I came along the following notes:

    Homologous series of alkanes
    Alkanes are saturated organic compounds
    Homologous series of alkenes
    Alkenes are unsaturated organic compounds

    Can you just describe the bold-italic words?

    Thanks.
    1) Homologous series - they are analogous to functional groups, ie what characterises a particular organic compound family

    2) saturated - single bonds between C-C

    3) unsaturated - opposite of saturated, more than a single bond between C-C, ie double in alkenes, triple in alkynes

    NB, you mention C-C because all C-H has to be single bonds due to H only having one electron to share in covalent bond
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    http://en.wikipedia.org/wiki/Homology_%28chemistry%29

    Saturated - no double bonds, single bonds

    Unsaturated - double bonds
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    Homologous series - A series of organic compounds with the same functionaly group, but with each successive member differing by CH2.

    Saturated - Single bonds in the hydrocarbon chain only.

    Unsaturated - A hydrocarbon containing at least one C=C double bond.

    Alkanes are saturated as they have single C-C and C-H bonds only.

    Alkenes are unsaturated as they have at least one C=C double bond in the chain.

    Hope this helps
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    (Original post by lattywatty)
    Homologous series - A series of organic compounds with the same functionaly group, but with each successive member differing by CH2.

    Saturated - Single bonds in the hydrocarbon chain only.

    Unsaturated - A hydrocarbon containing at least one C=C double bond.

    Alkanes are saturated as they have single C-C and C-H bonds only.

    Alkenes are unsaturated as they have at least one C=C double bond in the chain.

    Hope this helps
    Not necessarily a C-C double bond, alkynes (with a C-C triple bond) are also unsaturated.
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    (Original post by Stefan1991)
    Organic chemistry? Isn't that biology.
    Organic chemistry =/= biology
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    (Original post by Stefan1991)
    Organic chemistry? Isn't that biology.
    No, this is organic chemistry.
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    (Original post by shengoc)
    1) Homologous series - they are analogous to functional groups, ie what characterises a particular organic compound family

    2) saturated - single bonds between C-C

    3) unsaturated - opposite of saturated, more than a single bond between C-C, ie double in alkenes, triple in alkynes

    NB, you mention C-C because all C-H has to be single bonds due to H only having one electron to share in covalent bond
    Thanks for your reply.

    But, what is exactly meant by "saturated"? What made alkanes "saturated" and alkenes "unsaturated". The numbering of bonds is clear in both cases, but the case of "saturation" is not.
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    (Original post by lattywatty)
    Homologous series - A series of organic compounds with the same functionaly group, but with each successive member differing by CH2.

    Saturated - Single bonds in the hydrocarbon chain only.

    Unsaturated - A hydrocarbon containing at least one C=C double bond.

    Alkanes are saturated as they have single C-C and C-H bonds only.

    Alkenes are unsaturated as they have at least one C=C double bond in the chain.

    Hope this helps
    Thanks for your reply.

    What do you mean by ...successive member differing by CH2.

    And, can you just explain "saturation" in a bit more detail?
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    (Original post by SWEngineer)
    Thanks for your reply.

    What do you mean by ...successive member differing by CH2.

    And, can you just explain "saturation" in a bit more detail?
    By that I mean that the chain is increased by one carbon atom attached to two hydrogen atoms each time. E.g. butane differs from propane by CH2, and hexene differs from pentene by CH2.

    Saturation is defined as: soaked, impregnated, or imbued thoroughly; charged thoroughly or completely; brought to a state of saturation.

    So if you think about it, if each carbon atom has four bonds to other atoms, it has reached the maximum number of atoms it can have attached to it (as carbon has four electrons on its outer shell). This means it is saturated.

    However, if there is a double bond then it may only be attached to three atoms therefore it is not fully saturated as more atoms can still be added to the atom before it reaches its maximum.
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    (Original post by lattywatty)
    By that I mean that the chain is increased by one carbon atom attached to two hydrogen atoms each time. E.g. butane differs from propane by CH2, and hexene differs from pentene by CH2.

    Saturation is defined as: soaked, impregnated, or imbued thoroughly; charged thoroughly or completely; brought to a state of saturation.

    So if you think about it, if each carbon atom has four bonds to other atoms, it has reached the maximum number of atoms it can have attached to it (as carbon has four electrons on its outer shell). This means it is saturated.

    However, if there is a double bond then it may only be attached to three atoms therefore it is not fully saturated as more atoms can still be added to the atom before it reaches its maximum.
    Thanks again so much.

    Just a small thing. Can you just give me an example of how alkanes are saturated and alkenes are unsaturated? Just to understand it better.
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    (Original post by SWEngineer)
    Thanks again so much.

    Just a small thing. Can you just give me an example of how alkanes are saturated and alkenes are unsaturated? Just to understand it better.
    saturated means no multiple bonds. So alkanes are saturated.

    alkenes, alkynes have mutliple bonds and so are unsaturated
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    (Original post by SWEngineer)
    Thanks again so much.

    Just a small thing. Can you just give me an example of how alkanes are saturated and alkenes are unsaturated? Just to understand it better.
    saturated - single C-C bonds, difficult to functionalise, ie can't do electrophilic addition of HBr

    unsaturated - multiple bonds between C-C, easy functionalisation, ie can do electrophilic addition, that is can still add across the multiple bonds till the C-C gets saturated

    hope that example clarifies the idea
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    (Original post by shengoc)
    saturated - single C-C bonds, difficult to functionalise, ie can't do electrophilic addition of HBr

    unsaturated - multiple bonds between C-C, easy functionalisation, ie can do electrophilic addition, that is can still add across the multiple bonds till the C-C gets saturated

    hope that example clarifies the idea
    Is tere a simpler example that shows how is this shown in the alkanes and alkenes organic compounds (i.e; methane, methene)?
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    (Original post by SWEngineer)
    Is tere a simpler example that shows how is this shown in the alkanes and alkenes organic compounds (i.e; methane, methene)?
    you cannot get "methene", as that would violate that C-H must be single bonds.
    simplest alkene is ethene, 2 carbons where you can have double bonds between C-C

    are you sure you understand bonding?
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    (Original post by SWEngineer)
    Is tere a simpler example that shows how is this shown in the alkanes and alkenes organic compounds (i.e; methane, methene)?
    how could you have methene? Methane only has one carbon!

    (saturation/unsaturation refers to carbon to carbon bonds, hence the simplest compound that can be unsaturated is one with two carbons, ethene)
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    (Original post by shengoc)
    you cannot get "methene", as that would violate that C-H must be single bonds.
    simplest alkene is ethene, 2 carbons where you can have double bonds between C-C

    are you sure you understand bonding?
    Yes, I understand bonding, but seems I mentioned "methene" without paying attention to the existence of at least two carbons where the double bonds will be between.
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    (Original post by SWEngineer)
    Yes, I understand bonding, but seems I mentioned "methene" without paying attention to the existence of at least two carbons where the double bonds will be between.
    there is something called methylene, though (:CH2) but it's a diradical and you really don't want to worry about that! :no:
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    (Original post by CitizensUnited)
    Organic chemistry =/= biology
    (Original post by SWEngineer)
    No, this is organic chemistry.
    Fair enough, but what is the difference?
 
 
 
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