10 - ORGANOSULFUR CHEMISTRY Flashcards
what group does sulfur belong to?
chalcogen group (“oxygen family”)
expected that organosulfur compounds have similarities to carbon oxygen compounds, but that is true to some extent
what are the two sulfur amino acids?
methionine and cysteine
what is prontosil?
what is alliin and what does it cause?
derived from cysteine
what is skunk spray made of?
mainly made of low molecular weight thiols which are detectable at concentrations of about 2 parts per million
(E)-2-butene-1-thiol
3-methyl-1-butanethiol
(E)-2-butene-1-thioacetate
how can skunk smell be removed? (example with (E)-2-butene-1-thiol
turn the compounds into sulfonic acids
you need H2O2, baking soda, dishwashing detergent
what is mercaptan structure and what it does
grapefruit mercaptan: scent of grapefruit
used in perfume and flavor industry
this aroma is only a property of the R stereoisomer
what are some benefits of bad smelling sulfides?
used to scent natural gas so that gas leaks are easily detectable
what does phosphorus exist as?
exists as P4
what does sulfur exist as?
exists as S8
does not have the tendency as N and O to make double bonds
why does oxygen exist as a double bond but sulfur cannot do that?
Nitrogen and Oxygen use 2p orbitals to form pi bonds
P and S use 3p orbitals to form pi bonds
the orbitals are larger which means that there is a larger interatomic distance, and therefore a weaker 3p-3p overlap
that is why P4 and S8 exist as single bonds
why are C=S bonds relatively weaker and what does this explain?
weak overlap because of the size differences between 2p and 3p pi orbitals
this explains why ene-thiols are the favored form over thiones because ene-thiols have a C=C double bond instead of a C=S bond
how many valence electrons does sulfur have?
6 valence electrons, uses s, p and d orbitals in bonding
hypervalent molecule, can have more than 8 electrons in its shell
draw the normal electron configuration vs hybridized electron configuration of sulfur
what can SF6 gas be used for?
high density, was put into shoes to give it more bound but it is a greenhouse gas so it hasnt been used anymore
if you inhale SF6 it gives you a deep voice
how does SF4 arrange?
what about phosphorus orbitals, PF5 and PF6-?
phosphorus also uses s, p and d orbitals in bonding
how can there be some p-d pi bonding and what is the evidence for that?
bond length is shorter than expected for the P-O or S-O single bond
the structure with a negative oxygen has a tetrahedral arrangement like an sp3 carbon
what do the orbitals look like when you make a S-O sigma bond or S=O pi bond?
structure of a thiol
structure of a sulfide
structure of a disulfide
what are some examples of naturally occuring thiols?
how do thiols scavenge hydroxyl radicals?
how do two thiols oxidise?
how does 2R-SH + X2 react?
2R-SH +X2-> RSSR+2HX
how does nucleophilicity of sulfur compare to alcohol oxygen?
sulfur atom in a thiol is more nucleophilic than the alcohol oxygen
+ sulfur is less electronegative and holds onto its electrons less tightly than oxygen
charge from the TS is better accommodated
also, thiolate ions are less solvate
this is an example of how thiolates (negative charge on sulfur) are weaker bases but more nucleophilic than alkoxide
what is the problem when you try to make thiols with NaSH?
hard to control, results in overalkylation
how can the problem of overalkylation be fixed?
use thiourea instead of NaSH followed by OH- and acidic workup
how are alkyl halides (RX) made?
how are aromatic thiols made from diazonium salts?
what is a mechanism for making aromatic thiols from diazonium salts?
how is Me-S-Me made from Me-SH?
how is a cyclohexane thiol made into a sulfide?
how is an episulfide ring formed?
synthesis of unsymmetrical sulfides and why is it an SN2 reaction?
