Determining the R and S configurations about a stereocenter
Tim McLaurin-Avril Lavigne Method
Quick Overview of Steps
1. Make sure the organic structure has at least one (1) stereocenter.
2. Assign priorities to the 4 different elements/groups bonded to the stereocenter.
3. Rotate from Highest priority to Lowest priority and note the direction of rotation, as left or right.
4. Depending upon whether the rotation is to the Left or to the Right will designate the stereocenter
as a S or a R configuration, respectively.
5. Name the stereocenter, using the Tim McLaurin-Avril Lavigne method, with R or S.
6. Using the IUPAC nomenclature rules, name the entire structure and designate the stereocenters
as R or S.
Significance of the Tim McLaurin-Avril Lavigne Method
1. The Study of Organic Chemistry has existed for a little more than 220 years.
2. Around 1986, there was only one (1) method using one's hands, fingers, wrists, that had been
developed to determine whether the stereocenter was the R or S configuration.
3. According to the Organic Textbooks, the individual who developed this method was the Only
individual to ever develop a method using one's fingers, hands, wrists, and arms, and the Only
individual noted in the Organic Chemistry Textbooks to have ever developed such as method.
4. The name of the Scientist who developed the method was Huheey.
a. The method requires that the student use both hands, or at least, the visualization of both
right and left hands, including the wrist(s).
b. The method also requires the use of the 1st three (3) fingers of either the right or left hand.
The thumb, the index finger, and the middle finger. Thus, spanning only 1/2 of the wrist.
5. I developed another method, hopefully to be in print in the Organic Chemistry Textbooks in the
future, using different fingers (the thumb, the index finger, and the pinky finger, as well as, using the
forearm). The following provides the advantages of the method versus Huheey's method and
examples are provided, thereafter. Avril Lavigne, as mentioned above, was helpful and
instrumental in the development of this method and the name of the method is shared with Avril
Lavigne, rightfully so.
6. The Tim McLaurin-Avril Lavigne method has distinct advantages over Huheey's Method and are
as follows:
a. The method requires that the student use only one (1) hand, which can be either the right or
left hand. Noting, handicapped individual's with only one (1) hand, can use this method.
b. This method, as well as Huheey's method, requires the use of three (3) fingers. Yet, this
method uses the fingers that span the entire hand and wrist, thus providing the student with a
more realistic imagery of the structure, from the fingers, to the wrist, to the forearm.
c. The 'World-Wide' positive gesture (International Sign Language), that the extended fingers
represents, is frequently encountered with the activities of the 'Student's of Today', and to a
smaller extent 'Today's Society', in America and throughout the World.
Example #1
Determining R or S configuration, when a structure
has one (1) stereocenter and the lowest priority group is directed away from the viewer.
1. Structure A has one (1) stereocenter. Structure B has designated the priority sequence to every
element and/or group bonded to the stereocenter using the letters a, b, c, d. (a has the Highest
priority). Structure C has not been rotated so that the Lowest priority element and/or group is
directed away from the viewer (the lowest priority group is already directed away from the
viewer), therefore, Structure C is identical as Structure B. Structure D has arrows pointing in the
direction of rotation from the Highest priority element and or group to the second (2nd) highest
element/group. Structure E has been named according to the direction of the arrows associated
with Structure D.
Figure-1
*Rules associated with the Tim McLaurin-Avril Lavigne method of RS designation:
1. The pinky finger is always pointed away from the viewer to start with.
2. The thumb, the index finger, & the pinky finger, are the fingers used for this method.
3. The thumb, the index finger, & the pinky finger, are extended up & out away from the wrist.
4. The middle finger and the ring finger are always closed to the palm of the hand.
Same Example #1 as above, yet using the Tim McLaurin-Avril Lavigne method
(photos of fingers, hand, wrist, and forearm are provided) when
a structure has one (1) stereocenter and the lowest priority
group is directed away from the viewer.
Figure-2: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
*The same hand gesture is used for all of the above structures, including structures D and E.
Photo-1A-1 (using the Right Hand) Photo-1A-2 (using the Left Hand)
*Photos throughout the following examples use the right hand, until noted otherwise.
1. Using the letters a, b, c, d, to designate the priority from Highest to Lowest. The pinky finger
always has the lowest priority, to start with. This method requires that the Lowest priority element
and/or group be directed away from the viewer. In the above photo, the pinky finger is directed
away from the viewer, therefore has the lowest priority. The thumb, the index finger, and the
forearm, act as the other three (3) elements and/or groups bonded to the stereocenter (usually a
carbon element). The wrist, itself, is the element that has four (4) different elements and/or groups
bonded to it, and is occasionally called the stereogenic carbon.
2. In the above example ((R)-bromochlorofluoromethane), the pinky represents the Hydrogen
element, which has the lowest priority and direct farthest from the viewer. The thumb represents
the bromine element (the Highest priority) and represented as the 'a' element in the priority
sequence. The index finger represents the chlorine element and the forearm represents the fluorine
element. The fluorine element is designated as 'c' in the priority sequence, because it has the next
to lowest priority.
3. Therefore, looking at the above photo of a hand, the priority sequence goes from the thumb to the
index finger to the forearm. The clockwise direction (R direction). Therefore, the configuration
would be designated as the R. Thus, the correct IUPAC name of the organic structure is
(R)-bromochlorofluoromethane.
Example #2
Determining R or S configuration, when a structure
has one (1) stereocenter and the lowest priority group is Not directed away from the viewer.
1. Structure A has one (1) stereocenter. Structure B has designated the priority sequence to every
element and/or group bonded to the stereocenter using the letters a, b, c, d. (a has the Highest
priority). Structure C has been rotated so that the Lowest priority element and/or group is
directed away from the viewer. Structure D has arrows pointing in the direction of rotation from
the Highest priority element and or group to the second (2nd) highest element/group. Structure E
has been named according to the direction of the arrows associated with Structure D (of which is,
counterclockwise, to the left, therefore the S configuration).
Figure-3: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
The same rules apply as stated earlier and are stated once again, as follows:
*Rules associated with the Tim McLaurin-Avril Lavigne method of RS designation:
1. The pinky finger is always pointed away from the viewer to start with.
2. The thumb, the index finger, & the pinky finger, are the fingers used for this method.
3. The thumb, the index finger, & the pinky finger, are extended up & out away from the wrist.
4. The middle finger and the ring finger are always closed to the palm of the hand.
Same Example #2 as stated above, yet using the Tim McLaurin-Avril Lavigne method
(photos of fingers, hand, wrist, and forearm are provided) when
a structure has one (1) stereocenter with the lowest priority
group Not directed away from the viewer.
1. Note that the lowest priority element/group is Not directed away from the viewer, yet using the
Tim McLaurin-Avril Lavigne method, start out with the hand and fingers as depicted in photo-2
and rotate your hand as depicted in photo-3 and then photo-4. Therefore, placing the Lowest
priority element/group Farthest from the viewer, thus leaving the three (3) Highest priority
elements forward, toward the viewer. (NOTE: Photo-1A, shown earlier, and Photo-2 are the
same photo's, only to make things easier to take note of)
Figure-4: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
Figure-5: Rotating structure so that H (lowest priority) is farthest from viewer.
Photo-2 Photo-3 Photo-4
2. After rotating your hand in the manner as depicted in photo's 2, 3, and 4, the Lowest priority
element (Hydrogen) is your index finger and farthest from you, the viewer. The Highest priority
elements/groups are forward and pointing toward you, that is, the Highest priority sequence of a
to b to c. Those three (3) elements/groups representing a to b to c , for this example #2, are as
follows:
Photo-5A-1
(Same as photo-4, yet has curved arrows)
a = Bromine = Highest priority = the Thumb
b = Chlorine = 2nd highest priority = the Pinky finger
c = Fluorine = 3rd highest priority = the Forearm
3. Looking at your hand, as depicted in Photo-5 (or Photo-4), going from a to b to c (from your
thumb to your pinky finger to your forearm, is going in the counterclockwise (Left) direction.
The S configuration about a stereocenter goes in the counterclockwise (Left) direction,
therefore the stereocenter is the S configuration. The correct IUPAC name of the structure for
this example (example #2) is: (S)-Bromochlorofluoromethane.
4. The following photo (photo5A-2), is the same as the above photo-5A-1, yet includes three (3)
structures of (S)-Bromochlorofluoromethane, side by side, with the photo of the hand, fingers,
wrist, and forearm.
Photo-5A-2
(Same as photo-5A-1, yet has the same structures written different ways)
(The two (2) structures to the right of Photo-5A-2 use the rotated hand and fingers, to determine the R or S nature of the stereocenter. The following structures use a different rotation of the hand and fingers to determine the R or S configuration about the stereocenter. Yet, the two (2) structures above and the next three (3) structures, all represent (S)-BromoChloroFluoromethane!
Example #3
Determining R or S configuration, when a structure has one (1) stereocenter
and the lowest priority group is Not directed away from the viewer, yet directed
in the opposite direction versus Example #2.
1. Structure A has one (1) stereocenter. Structure B has designated the priority sequence to every
element and/or group bonded to the stereocenter using the letters a, b, c, d. (a has the Highest
priority). Structure C has been rotated so that the Lowest priority element and/or group is
directed away from the viewer. Structure D has arrows pointing in the direction of rotation from
the Highest priority element and or group to the second (2nd) highest element/group, to the third
(3rd) highest element. Structure E has been named according to the direction of the arrows
associated with Structure D (of which, is counterclockwise, to the left, therefore the S
configuration).
Figure-6: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
The same rules apply as stated earlier and are stated once again, as follows:
*Rules associated with the Tim McLaurin-Avril Lavigne method of RS designation:
1. The pinky finger is always pointed away from the viewer to start with.
2. The thumb, the index finger, & the pinky finger, are the fingers used for this method.
3. The thumb, the index finger, & the pinky finger, are extended up & out away from the wrist.
4. The middle finger and the ring finger are always closed to the palm of the hand.
Same Example #3 as stated above, yet using the Tim McLaurin-Avril Lavigne method
(photos of fingers, hand, wrist, and forearm are provided) when
a structure has one (1) stereocenter with the lowest priority
group Not directed away from the viewer.
1. Note that the lowest priority element/group is Not directed away from the viewer, yet using the
Tim McLaurin-Avril Lavigne method, start out with the hand and fingers as depicted in photo-6
and rotate your hand as depicted in photo-7 and then photo-8. Therefore, placing the Lowest
priority element/group Farthest from the viewer, thus leaving the three (3) Highest priority
elements forward (backside of hand) to the viewer. (NOTE: Photo's - 1A, 2, and Photo-6
are the same photo's, only to make things easier to take note of)
Figure-7: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
Figure-8: Rotating structure so that H (lowest priority) is farthest from viewer.
Photo-6 Photo-7 Photo-8
2. After rotating your hand in the manner as depicted in photo's 6, 7, and 8, the Lowest priority
element (Hydrogen) is your thumb. Photo-8 depicts your thumb as located farthest from
you, the viewer, and your thumb is not viewable with your hand in that rotated position. The
Highest priority elements/groups are forward (on the side of your viewable hand after you have
rotated your hand, as in Photo-8). That leaves the Highest priority sequence of a to b to c.
Those three (3) elements/groups representing a to b to c , for this example #3, are as
follows:
Photo-9
(Same as photo-8, yet has curved arrows)
a = Bromine = Highest priority = the Index finger
b = Chlorine = 2nd highest priority = the Pinky finger
c = Fluorine = 3rd highest priority = the Forearm
3. Looking at your hand, as depicted in Photo-9 (or Photo-8), going from a to b to c (from your
index finger to your pinky finger to your forearm, is going in the clockwise (Right) direction.
The R configuration about a stereocenter goes in the clockwise (Right) direction, therefore the
stereocenter is the R configuration. The correct IUPAC name of the structure for this example
(example #3) is: (R)-Bromochlorofluoromethane.
Example #4
Determining R or S configuration, when a structure has one (1) stereocenter
and the lowest priority group is Not directed away from the viewer, yet directed
downward in relation to the other three (3) substitutents.
1. Structure A has one (1) stereocenter. Structure B has designated the priority sequence to every
element and/or group bonded to the stereocenter using the letters a, b, c, d. (a has the Highest
priority). Structure C has been rotated so that the Lowest priority element and/or group is
directed away from the viewer. Structure D has arrows pointing in the direction of rotation from
the Highest priority element and or group to the second (2nd) highest element/group, to the third
(3rd) highest element. Structure E has been named according to the direction of the arrows
associated with Structure D (of which, is counterclockwise, to the left, therefore the S
configuration).
Figure-9: Hydrogen has the lowest priority.
The same rules apply as stated earlier and are stated once again, as follows:
*Rules associated with the Tim McLaurin-Avril Lavigne method of RS designation:
1. The pinky finger is always pointed away from the viewer to start with.
2. The thumb, the index finger, & the pinky finger, are the fingers used for this method.
3. The thumb, the index finger, & the pinky finger, are extended up & out away from the wrist.
4. The middle finger and the ring finger are always closed to the palm of the hand.
Same Example #3 as stated above, yet using the Tim McLaurin-Avril Lavigne method
(photos of fingers, hand, wrist, and forearm are provided) when
a structure has one (1) stereocenter with the lowest priority
group Not directed away from the viewer.
1. Note that the lowest priority element/group is Not directed away from the viewer, yet using the
Tim McLaurin-Avril Lavigne method, start out with the hand and fingers as depicted in photo-
10 and rotate your hand to the position as depicted in photo-11. Therefore, placing the Lowest
priority element/group Farthest from the viewer, thus leaving the three (3) Highest priority
elements forward (and sort of pointing) at the viewer. (NOTE: Photo's - 1A, 2, 6, and 10 are
the same photo's, only to make things easier to take note of)
Figure-10: Hydrogen has the lowest priority & rotated farthest away from
the viewer.
Figure-11: This figure does provide a way of moving elements around and then
use the Tim McLaurin-Avril Lavigne method, yet there is a much
easier way, by the use of the Tim McLaurin-Avril Lavigne method
without rotating any elements!
2. Considering hydrogen is the lowest in the priority sequence and it is pointing downward, note
the following illustration and photo's-10 & 11 on both sides of the structure. You should note
how easier it is to determine the R or the S configuration about the stereocenter, using the Tim
McLaurin-Avril Lavigne method in the following photo's. (The forearm is assigned the lowest
priority element, that is, hydrogen)
Photo-10 Photo-11
3. Assigning the priority sequence to photo-11 provides the correct R or S configuration about a
stereocenter, as illustrated in the next photo, photo-12.
Photo-12
4. Note the Lowest priority element is Hydrogen, which is represented by the forearm, and
remains in place, yet when turning (rotating) the wrist, in order to view the three (3) highest
priority elements, the thumb, the index finger, and the pinky, have rotated 1200 . Therefore, the
three Highest priority elements are located in the positions as depicted in photo-12. The
rotation is counterclockwise, therefore the S configuration.
Structures with more than one (1) stereocenter and the Fischer Projection
using the Tim McLaurin-Avril Lavigne Method
1. The Tim McLaurin-Avril Lavigne method does work for structures with more than one (1)
stereocenter. Whether the structures are straight or branched chains or single or poly-ring(s), with
multiple stereocenters, this method does work for those multiple stereocenter structures. In
addition, the Tim McLaurin-Avril Lavigne method does work with the 'Fischer projections'. It is
Much Easier using the Tim McLaurin-Avril Lavigne method in conjunction with the Fischer
Projections, than any method that I have found and used, since 1982. And the same conclusion,
as a student of Organic Chemistry, will agree, to the ease of use of the Tim McLaurin-Avril
Lavigne method and determining the R or S configuration about the stereocenters on the Fischer
Projection.
2. Unfortunately, I must not provide those examples using the Tim McLaurin-Avril Lavigne method
on this website (webpage), due to the possibility of this method being printed in one or more
Organic Chemistry Textbooks. The places (websites) that this website will be exposed to, keep
an archive, many for years, and to divulge the information would be to decrease my chances and
Avril Lavigne's chances of this method being printed in the Textbooks, or my chances and Avril
Lavigne's chances, of the possibility, of the sale of this information to the textbooks.
3. Yet, I will make mention of the following, if you can work your way through the 4 examples listed
above, you will have learned enough information to determine for yourself, how the Tim
McLaurin-Avril Lavigne method works with multiple stereocenters and especially, the Fischer
projection.
4. I hope you have found this website of interest, exciting, useful in your studies of Organic
Chemistry, in addition, that this website has kept your attention and the Tim McLaurin-Avril
Lavigne method to be of use now and in the future.