Synthetic routes and bond angles

AsBr2008

Doing OCR A-level chemistry. How the hell do I memorise synthetic routes and bond angles??

Reply 1

Brute force and repetition is how I’m doing it and I’m reasonably good already, I only stated revising a couple of weeks ago

Reply 2

TypicalNerd

Original post by AsBr2008

Doing OCR A-level chemistry. How the hell do I memorise synthetic routes and bond angles??

OCR has a complete organic synthesis map, along with a blank copy for you to fill in yourself:

https://www.ocr.org.uk/Images/359182-organic-synthesis-reaction-pathways.pdf

As for bond angles, I suggest drawing up a table like the one below:

Basically do as suggested above, but by using the blank synthetic maps included in the link and for the bond angles, try reproducing the above table from memory.

(Edit: note that OCR expects you to learn the tetrahedral bond angle as 109.5° and the bond angle in the 2 bonding pairs + 2 lone pairs form of the bent shape as 104.5°. Additionally, you need not worry about memorising square pyramidal, seesaw or t-shaped geometries)

(edited 1 month ago)

Reply 3

AsBr2008

Original post by TypicalNerd

OCR has a complete organic synthesis map, along with a blank copy for you to fill in yourself:
https://www.ocr.org.uk/Images/359182-organic-synthesis-reaction-pathways.pdf
As for bond angles, I suggest drawing up a table like the one below:

Basically do as suggested above, but by using the blank synthetic maps included in the link and for the bond angles, try reproducing the above table from memory.
(Edit: note that OCR expects you to learn the tetrahedral bond angle as 109.5° and the bond angle in the 2 bonding pairs + 2 lone pairs form of the bent shape as 104.5°. Additionally, you need not worry about memorising square pyramidal, seesaw or t-shaped geometries)

Thank you.

Reply 4

Pigster

Original post by AsBr2008

Doing OCR A-level chemistry. How the hell do I memorise synthetic routes and bond angles??

You only have to be able to explain six shapes:
octahedral 6bp 0lp 90o
tetrahedral 4bp 0lp 109.5o
trig. planar 3bo 0lp 120o
pyramidal 3bp 1lp 107o
linear 2bp 0lp 180o
bent usually 2bp 2lp 104.5o, but it can be 2bp 1lp (which would be around 117.5o, but you shouldn't be asked this angle, just the shape).

Essentially it is the shapes possible by period 2 compounds/ions; where the period 2 element is in the middle, e.g. NH2^+ AND octahedral

Also... if there is one or more double bond/s, ensure you don't talk about bond pairs, talk about bond regions, but explain it in the usual way: either state bond pairs/regions repel to maximum distance (if no lone pairs) or state lp repel more than bp.