Let's talk about naming aldehydes. So if the aldehyde functional group is your highest priority
group among all the groups in your compound then we're going to name that compound as an aldehyde
parent chain with the suffix -al at the end of the name if there's a higher priority group on
this list that's in your compound we'll name it as say an ester and acid halide or an amide one
of those higher priority groups is the parent chain and then the aldehyde will be subjugated
to a normal group if it's included in the parent chain it will be an oxo- group and if it's off of
the parent chain that aldehyde will be a formyl- group okay so we're gonna be careful every time
we name systematically to circle the parent chain on our paper we're gonna write the names of the
subordinate groups that intersect that circle to be careful again number the chain so that
the right numbers end up at the right groups and we're going to assemble the name checking
for stereochemistry to make sure we don't miss out anything in our name so let's practice where the
aldehyde is the highest priority group so it's got to be included in the parent chain and we're gonna
get as many alkenes and alkynes as we can here we can get all of them and we end up with one
group intersecting the parent chain that alcohol is a priority group unless it's in the presence
of something higher. Aldehyde's higher and so we're gonna end up subjugating this alcohol to a hydroxy-
group. Whenever alkenes and alkynes appear in the parent chain they get special treatment they get
the suffixes "en-yn" in that order with the final group being the highest priority group so
en-yn-ols, en-yn-amines, en-yn-al in this case and so we'll put numbers where appropriate now on
these groups the highest priority group gets the lowest number automatically 1-2-3-4-5
and 6 overall here. We do have two elements of stereochemistry one's a chiral center at carbon
two oxygen being the the highest-ranked group with the greatest atomic number of the first
atom attached then carbon to two oxygens beats carbon to two carbons hydrogen's going back is
group four where it's supposed to be for our assessment of R and S that's clockwise so
this is a 2R stereocenter and then next door we have an E opposite sides with the highest-ranked
group double bond so if we're going to put this name together we'll include that stereochemistry
out front and first in our name and in order of appearance we have a 2R we don't need the
2 because there's no confusing R's and E's double bonds and chiral centers okay so
we have (R,E) in order of appearance and then the only group intersecting the parent change
circle is the hydroxy group it's a 2-hydroxy and then finally six carbons is a hex- how many
or where are our locants for our priority groups here inside this circle we have an "-ene" a
3-en and a 5-yn and then the highest-ranked group is an -al we don't need a number because aldehydes
are always at the beginning of a parent chain when they're the highest priority group so it's
redundant to put the 1 we leave that all so -en-yn-al, 3-en-5-ynal we could also have written this
with the first locant of the suffixes here out front hexene, 3-hexen-5-ynal with a dash separating all
letters and numbers. Now when multiple aldehydes are present such as this first example here a
simple one we number our chain it's symmetrical either way left or right and it's a pentane
instead of pentanal we have a pentanedial so the "e" goes into separate the consonants "n"
and "d" to make it easier to say okay we look at our next example here we've got a little more
complicated of a group so I'm going to go ahead and circle the highest priority groups these two
aldehydes make sure they're in our parent chain any group intersecting the circle gets a name
and then we have stereochemistry in our double bonds we have an (E) here with opposite groups
in the trans position and on the left hand side we've got chlorine as a high-ranked besides
carbon what has a higher atomic number and then carbon versus hydrogen high and low that's a (Z)
stereocenter so we'll include those in this name as well so let's put this name together here okay
if we can get out there perfect so out in front we've got two elements of the same stereochemistry
so we do need numbers now I'm gonna go ahead and number this parent chain here to put the
lower number on the first encountered groups 1-2 is a tie with numbering for the alkenes and
aldehydes we can go 1-2 either way 1-2-3-4 either way so 1-2-3 lowers
the chlorine that's our next tiebreaker there to make sure we get the right numbers in our
name okay and so we're gonna start by putting the stereochemistry in here at the proper positions that's
a (2Z,4E) looks like we've got a chloro so a 3-chloro intersecting the circle and then
with two alkenes we have a hexa-2,4-diene and then a dial because of the dial we need an "e"
to separate the consonants "n" and "d" so we put the "e" back in 2,4-dienedial it's given that the
aldehydes begin and end the parent chain and so we've got everything there located we could have
also have again brought the numbers out front for the first suffix our 3-chloro doesn't change only
the parent chain ordering here the 2,4 can come out and we'll put hexadienedial again that
"a" goes in there to separate the "x" and the "d" is well there that's a convention from alkene and
alkyne nomenclature as well. All right suppose the aldehyde is not the highest priority group
here we have a nitrile that is and so now that aldehyde doesn't go into our circle it's a group
and it's an oxo- group the hydrogens trivial doesn't need a group name okay oxo does need
a group name and it's the aldehyde being part of the parent chain 1-2-3-4-5 carbon
five of the parent chain it's an oxo- group not a formal group the 1 of the nitrile goes in
for nitrile nomenclature so we'd call this a 5-oxo no stereochemistry to be had pentane
nitrile, 5-oxopentanenitrile. If the aldehyde is not on the parent chain and so the longest carbon
to carbon chain containing the highest priority group here our carboxylic acid is greater than
our aldehyde just like in the previous example our nitrile was greater than the aldehyde we
would get the longest carbon to carbon chain that has that highest priority group so we put
1-2-3-4 and a 5 and now because we're off the parent chain that carbon needs to be
needs to be named formyl it doesn't get a-, it's not included in the number of the
parent chain so it needs a full group name there it's a formal group. No stereochemistry indicated
at that chiral center so we don't have to worry about it, it's a 2-formylpentanoic acid two words
there for pentanoic acid named as a carboxylic acid because that's the highest priority group.