Question: I recently used the website <https://www.bitbrothersllc.com/Bitbrothersllc/Welcome.html> to obtain my bitcoins, but when I was asked what address to send my coins to, I accidentally put down my wallet's private key, not my bitcoin address.

I'm wondering if the coins are lost forever now, or if they will still appear in my wallet because the private key is attached to my address. I'm really hoping they are not lost forever, and I would greatly appreciate any assistance anyone could provide.

Answer: 
A **private key** can be encoded in a number of different formats:

* **51 characters** base58, starts with a '5' 
(for example: `5JrnhhNpRNsC6xPUhLfc4yJEviuRxMcvpcB4pc1opgHTSVi64aP`)
* **64 characters** [0-9A-F] hexadecimal format, 
for example: `89609C6B52AE0061FB8FFE3AF83528AC24AC637A386FE61D2822128ABE80162F`
* **44 characters** base64,
for example: `iWCca1KuAGH7j/46+DUorCSsY3o4b+YdKCISir6AFi8=`
* **52 characters** base58, WIF Compressed, starts with a 'K' or 'L', 
for example: `L1pkidDJJbWY1HUDF3oPnXV6U7xR9L1aZ8FRs7YZfSPdh5NPzRB5`

A bitcoin **address**, which is a *hash* of the public key, is **25-34 characters**, [typically 34 characters](https://web.archive.org/web/20191225180429/https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses),
for example: `1A5QMFw4vXVwLF1zZMSvAYJStuVMcjSqAa`

Maybe a bitcoin address *could* be encoded in some other format, but 25-34 characters of base58 is the standard.

I don't know what kind of validations are in place at *bitbrothersllc*, but they should easily be able to see that you entered 51, 64, 44, or 52 characters instead of the 25-34 characters that would make up a valid bitcoin address. 

Contact them. If they are legit, you'll get your funds back. Good luck!
You can't send to a private key, that would be invalid in any client. You have exposed your private keys to a third party though, which you need to rectify immediately.