Term
| how the the carbons in benzene hybridised? |
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Definition
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Term
| what is the bond angle of a carbon that is sp3 hybridised? what is the shape of this molecule? |
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Definition
109.5 degrees
shape is tetrahedral |
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Term
true or false?
saturated carbon atoms are sp3 hybridised? |
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Definition
| this is true Px Py and Pz orbitals are in use |
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Term
| a carbon has .... valence orbitals and .... valence electrons |
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Definition
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Term
| any carbon forming 1 double bond and 2 single bonds is trigonal planar but what is the bond angle and what is the carbon hybridisation? |
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Definition
bond angle 120 degrees
sp2 hybridisation eg. alkenes like propene |
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Term
| which p orbital is involved in making the pi (double bond) in sp2 hybrids? |
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Definition
| it is the last one Pz orbital. this is the unhybridised orbital. |
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Term
| in sp2 hybrids what are single bonds also known as? |
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Definition
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Term
| which type of bonds are formed from HEAD ON overlap of two sp2 hybrid orbitals? |
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Definition
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Term
true or false?
pi bonds are formed from SIDE ON overlap of the two Py orbitals? |
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Definition
| False! it is from the side on over lap of 2 Pz orbitals |
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Term
| the 2 electrons in a c-c pi bond are less stable. does this mean they are higher or lower in energy? |
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Definition
| they are higer in energy and more accesible that electrons in sigma bonds. this makes alkenes behave in an electron rich way |
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Term
| what do you call something with alternating double bonds that overlap to form an extended pi system? |
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Definition
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Term
| what reactions do alkenes and conjugated alkenes undergo? |
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Definition
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Term
| who first studied benzene? |
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Definition
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Term
| what are the bond angles in benzene and what is its geometry? |
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Definition
bond angle 120 degrees
planar geometry |
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Term
| benezene is unuasually stable due to which property? |
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Definition
| due to its resonance energy of approx 150KJ/mol |
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Term
| for any chemical species if more than one stable lewis structure can be drawn, what does this imply about its stability? |
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Definition
| that it will be more stable that otherwise expected |
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Term
| can the structure of benzene be represented by one localised lewis structure? |
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Definition
| no. it has resonance thus needs more than one lewis structure to show its structure. |
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Term
| the heat of hydrogenation of benzene is less than three times that of cyclohexene. what is this extra thermodynamic stability called? |
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Definition
| its resonance energy of approximatley 150kj/mol |
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Term
true or false?
aromatic compounds undergo electrophilic addition like alkenes? |
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Definition
| false, they undergo electrophilic substitution |
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Term
complete the definition of aromatic compounds:-
to be aromatic a compound must be ..................... and stabilised by a significant ............... energy |
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Definition
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Term
| what does the pi electron density form above and below the molecular plane of benzene? |
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Definition
| a torus (a revolving circle in 3 dimensional space) |
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Term
requirements for aromaticty
a continous ......... cyclic pi system is a necessary condition. but this is still not sufficient |
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Definition
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Term
| to be aromatic every atom in the ring must be sp2 hybridised. why? |
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Definition
| so it can contribute a P orbital to the cyclic pi system |
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Term
| can a compound be aromatic if the ring atoms are not all lying in one plane? |
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Definition
| no it cannot. this is one of Huckels criteria for aromaticity that the ring atoms must all lie in ONE plane |
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Term
| to be aromatic the pi system must contain a total of 4n +2 pi electrons. what does n stand for? |
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Definition
| it is an integer (whole number) |
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Term
| what is the difference betwen 14,16 and 18 Annulene? |
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Definition
14 and 18 are aromatic and planar
16 annulene is non planar and non aromatic |
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Term
| can compounds containing fused benzene rings still be aromatic? |
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Definition
yes silly course they can!
eg. Naphthalene
eg. Phenanthrene
eg.Anthracene |
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Term
| in fused rings are the pi electrons that are common to both rings shared or not shared? |
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Definition
| they are shared. each ring is considered to have an aromatic sextet by sharing these pi electrons |
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Term
| what is pyridine an example of ? |
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Definition
| a heterocyclic aromatic ring. |
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Term
| in pyridine what is the hybridisation of the Nitrogen? |
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Definition
sp2 hybridised.
its lone pair of electrons is in an sp2 orbital and NOT part of the pi system. |
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Term
| what is the difference between the nitrogen in pyridine and Pyrrole? |
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Definition
in pyridine the lp is NOT part of the pi system
in Pyrrole the lp IS part of the pi system |
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Term
| in a furan ring oxygen is present. oxygen has 2 lp of electrons. how many participate in the pi system? |
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Definition
| one pair is part of the pi system. the other pair in in an sp2 hybrid orbital and not part of the pi system |
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